AutoFS

AutoFS

• Automatically mount and unmount on clients during runtime and system reboots.
• Triggers mount or unmount action based on mount point activity.
• Client-side service
• Mount an NFS share on demand
• Entry placed in AutoFS config files.
• Automatically mounts share upon detecting activity in it’s mount point. (touch, ls, cd)
• unmounts share if the share hasn’t been accessed for a predefined period of time.
• Mounts managed with autofs should not be mounted manually via /etc/fstab to avoid inconsistencies.
• Saves Kernel from having to maintain unused NFS shares. (Improved performance!)
• NFS shares are defined in config files called maps (/etc/ or /etc/auto.master.d/)
• Does not use /etc/fstab.
• Does not require root to mount a share (fstab does).
• Prevents client from hanging if share is down.
• Share is unmounted if not accessed for 5 minutes (default)
• Supports wildcard characters or environment variables.
• Automount daemon
  • in the userland mounts configured shares automatically upon access.
  • invoked at system boot.
  • Reads AutoFS master map and create initial mount point entries. (not mounting yet)
  • Does not mount shares until user activity is detected.
  • Unmounts after set timeframe of inactivity.
• Use the mount command on a share to verify the path of the AutoFS map, file system type, and options used during mount.

/etc/autofs.conf/ preset Directives: master_map_name=auto.master timeout = 300 negative_timeout = 60 mount_nfs_default_protocol = 4 logging = none

Additional directives:

master_map_name

• Name of the master map. Default is /etc/auto.master timeout

• Time in second to unmount a share. negative_timeout

• Timeout (in seconds) value for failed mount attempts. (1 minute default) mount_nfs_default_protocol

• Sets the NFS version used to mount shares. logging

• Logging level (none, verbose, debug)

• Default is none (disabled)

• Normally left to their default values.

AutoFS Maps

• Where AutoFS finds the shares to mount and their locations.
• Also tells Autofs what options to use.

Map Types:

• master
• direct
• indirect

Master Map

Define entries for indirect and direct maps.

• /etc/auto.master is default
• Default is defined in /etc/autofs.conf with master_map_name directive.
• May be used to define entries for indirect and direct maps.
  • But it is recommended to store user-defined maps in /etc/auto.master.d/
    • AutoFS service parses this at startup.
• You can append an option to auto.master but it will apply globally to all subentries in the specified map file.

Map entry format examples:

  /-                      /etc/auto.master.d/auto.direct   \# Line 1

  /misc                   /etc/auto.misc                   \# Line 2

Direct Map

/- /etc/auto.master.d/auto.direct <-- defines direct map and points to auto.direct for details

Mount shares on unrelated mount points

• Always visible to users
• Can exist with an indirect share under one parent directory
• Accessing a directory containing many direct mount points mounts all shares.
• Each direct map entry places a separate share entry to /etc/mtab
  • /etc/mtab maintains a list of all mounted file systems whether they are local or remote.
  • Updated whenever a local file system, removable file system, or a network share is mounted or unmounted.

Indirect Map

/misc /etc/auto.misc <-- indirect map and points to auto.misc for details

Automount removable filesystems

• Mount point /misc precedes mount point entries in /etc/auto.miscq
• Used to automount removable file systems (CD, DVD, USB disks, etc.)
• Custom indirect map files should be located in /etc/auto.master.d/
• Preferred over direct mount for mounting all shares under one common parent directory.
• Become visible only after they have been accessed.
• Local and indirect mounted shares cannot coexist under the same parent directory.
• One entry in /etc/mtab gets added for each indirect map.
• Usually better to use indirect map for automounting NFS shares.

Lab: Access NFS Share Using Direct Map (server10)

1. Install Autofs

sudo dnf install -y autofs

1. Create mount point /autodir using mkdir

sudo mkdir /autodir

1. Add an entry to /etc/auto.master to point the AutoFS service to the auto.dir file for more information:

/- /etc/auto.master.d/auto.dir

1. Create /etc/auto.master.d/auto.dir and add the mount point, NFS server, and share info:

/autodir server20:/common

1. Start AutoFS service and enable it at startup:

sudo systemctl enable --now autofs

1. Make sure AUtoFS service is running. Use -l and –no-pager options to show full details without piping the output to a pager program (pg)

sudo systemctl status autofs -l --no-pager

1. Run ls on the mount point then verify the share is automounted and accessible with mount.

ls /autodir
mount | grep autodir

1. Wait 5 minutes and run the mount command again to see it has disappeared.

mount | grep autodir

Exercise 16-4: Access NFS Share Using Indirect Map

• configure an indirect map to automount the NFS share /common that is available from server20.
• install the relevant software and set up AutoFS maps to support the automatic mounting.
• Observe that the specified mount point “autoindir” is created automatically under /misc.

Note that /common is already mounted on the /local mount point via the fstab file and it is also configured via a direct map for automounting on /autodir. There should occur no conflict in configuration or functionality among the three.

1. Install the autofs software package if it is not already there:

2. Confirm the entry for the indirect map /misc in the /etc/auto.master file exists:

[root@server30 common]# grep ^/misc /etc/auto.master
/misc	/etc/auto.misc

3. Edit the /etc/auto.misc file and add the mount point, NFS server, and share information to it:

autoindir server30:/common

4. Start the AutoFS service now and set it to autostart at system reboots:

[root@server40 /]# systemctl enable --now autofs

5. Verify the operational status of the AutoFS service. Use the -l and --no-pager options to show full details without piping the output to a pager program (the pg command in this case):

[root@server40 /]# systemctl status autofs -l --no-pager

6. Run the ls command on the mount point /misc/autoindir and then grep for both auto.misc and autoindir on the mount command output to verify that the share is automounted and accessible:

[root@server40 /]# ls /misc/autoindir
test.text

[root@server40 /]# mount | egrep 'auto.misc|autoindir'
/etc/auto.misc on /misc type autofs (rw,relatime,fd=7,pgrp=3321,timeout=300,minproto=5,maxproto=5,indirect,pipe_ino=31779)
server30:/common on /misc/autoindir type nfs4 (rw,relatime,vers=4.2,rsize=262144,wsize=262144,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,clientaddr=192.168.0.40,local_lock=none,addr=192.168.0.30)

• /misc/autoindir has been auto generated.
• You can use the umbrella mount point /misc to mount additional auto-generated mount points.

Automounting User Home Directories \

AutoFS allows us to automount user home directories by exploiting two special characters in indirect maps.

asterisk (*)

• Replaces the references to specific mount points

ampersand (&)

• Substitutes the references to NFS servers and shared subdirectories.

• With user home directories located under /home, on one or more NFS servers, the AutoFS service will connect with all of them simultaneously when a user attempts to log on to a client.

• The service will mount only that specific user’s home directory rather than the entire /home.

• The indirect map entry for this type of substitution is defined in an indirect map, such as /etc/auto.master.d/auto.home.

* -rw &:/home/&

• With this entry in place, there is no need to update any AutoFS configuration files if additional NFS servers with /home shared are added or removed.

• If user home directories are added or deleted, there will be no impact on the functionality of AutoFS.

• If there is only one NFS server sharing the home directories, you can simply specify its name in lieu of the first & symbol in the above entry.

Exercise 16-5: Automount User Home Directories Using Indirect Map

There are two portions for this exercise. The first portion should be done on server20 (NFS server) and the second portion on server10 (NFS client) as user1 with sudo where required.

first portion

• create a user account called user30 with UID 3000.
• add the /home directory to the list of NFS shares so that it becomes available for remote mount.

second portion

• create a user account called user30 with UID 3000, base directory /nfshome, and no home directory.
• create an umbrella mount point called /nfshome for mounting the user home directory from the NFS server.
• install the relevant software and establish an indirect map to automount the remote home directory of user30 under /nfshome.
• observe that the home directory is automounted under /nfshome when you sign in as user30.

On NFS server server20:

1. Create a user account called user30 with UID 3000 (-u) and assign password “password1”:

[root@server30 common]# useradd -u 3000 user30
[root@server30 common]# echo password1 | sudo passwd --stdin user30
Changing password for user user30.
passwd: all authentication tokens updated successfully.

2. Edit the /etc/exports file and add an entry for /home (do not modify or remove the previous entry): /home server40(rw)

3. Export all the shares listed in the /etc/exports file:

[root@server30 common]# sudo exportfs -avr
exporting server40.example.com:/home
exporting server40.example.com:/common

On NFS client server10:

1. Install the autofs software package if it is not already there: dnf install autofs

2. Create a user account called user30 with UID 3000 (-u), base home directory location /nfshome (-b), no home directory (-M), and password “password1”:

[root@server40 misc]# sudo useradd -u 3000 -b /nfshome -M user30
[root@server40 misc]# echo password1 | sudo passwd --stdin user30

This is to ensure that the UID for the user is consistent on the server and the client to avoid access issues.

3. Create the umbrella mount point /nfshome to automount the user’s home directory:

sudo mkdir /nfshome

4. Edit the /etc/auto.master file and add the mount point and indirect map location to it: /nfshome /etc/auto.master.d/auto.home

5. Create the /etc/auto.master.d/auto.home file and add the following information to it: * -rw server30:/home/&

For multiple user setup, you can replace “user30” with the & character, but ensure that those users exist on both the server and the client with consistent UIDs.

6. Start the AutoFS service now and set it to autostart at system reboots. This step is not required if AutoFS is already running and enabled. systemctl enable --now autofs

7. Verify the operational status of the AutoFS service. Use the -l and --no-pager options to show full details without piping the output to a pager program (the pg command): systemctl status autofs -l --no-pager

8. Log in as user30 and run the pwd, ls, and df commands for verification:

[root@server40 nfshome]# su - user30
[user30@server40 ~]$ ls
user30.txt
[user30@server40 ~]$ pwd
/nfshome/user30
[user30@server40 ~]$ df -h
Filesystem             Size  Used Avail Use% Mounted on
devtmpfs               4.0M     0  4.0M   0% /dev
tmpfs                  888M     0  888M   0% /dev/shm
tmpfs                  356M  5.1M  351M   2% /run
/dev/mapper/rhel-root   17G  2.2G   15G  13% /
/dev/sda1              960M  344M  617M  36% /boot
tmpfs                  178M     0  178M   0% /run/user/0
server30:/common        17G  2.2G   15G  13% /local
server30:/home/user30   17G  2.2G   15G  13% /nfshome/user30

EXAM TIP: You may need to configure AutoFS for mounting a remote user home directory.

NFS DIY Labs

Lab: Configure NFS Share and Automount with Direct Map

• As user1 with sudo on server30, share directory /sharenfs (create it) in read/write mode using NFS.

[root@server30 /]# mkdir /sharenfs
[root@server30 /]# chmod 777 /sharenfs
[root@server30 /]# vim /etc/exports

# Add -> /sharenfs server40(rw)

[root@server30 /]# dnf -y install nfs-utils
[root@server30 /]# firewall-cmd --permanent --add-service nfs
[root@server30 /]# firewall-cmd --reload
success

[root@server30 /]# systemctl --now enable nfs-server


[root@server30 /]# exportfs -av
exporting server40.example.com:/sharenfs

• On server40 as user1 with sudo, install the AutoFS software and start the service.

[root@server40 nfshome]# dnf -y install autofs

• Configure the master and a direct map to automount the share on /mntauto (create it).

[root@server40 ~]# vim /etc/auto.master
/- /etc/auto.master.d/auto.dir

[root@server40 ~]# vim /etc/auto.master.d/auto.dir
/mntauto server30:/sharenfs

[root@server40 /]# mkdir /mntauto

[root@server40 ~]# systemctl enable --now autofs

• Run ls on /mntauto to trigger the mount.

[root@server40 /]# mount | grep mntauto
/etc/auto.master.d/auto.dir on /mntauto type autofs (rw,relatime,fd=10,pgrp=6211,timeout=300,minproto=5,maxproto=5,direct,pipe_ino=40247)
server30:/sharenfs on /mntauto type nfs4 (rw,relatime,vers=4.2,rsize=262144,wsize=262144,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,clientaddr=192.168.0.40,local_lock=none,addr=192.168.0.30)

• Use df -h to confirm.

[root@server40 /]# df -h | grep mntauto
server30:/sharenfs      17G  2.2G   15G  13% /mntauto

Lab: Automount NFS Share with Indirect Map

• As user1 with sudo on server40, configure the master and an indirect map to automount the share under /autoindir (create it).

[root@server40 /]# mkdir /autoindir

[root@server40 etc]# vim /etc/auto.master
/autoindir /etc/auto.misc

[root@server40 etc]# vim /etc/auto.misc
sharenfs server30:/common

[root@server40 etc]# systemctl restart autofs

• Run ls on /autoindir/sharenfs to trigger the mount.

[root@server40 etc]# ls /autoindir/sharenfs
test.text

• Use df -h to confirm.

[root@server40 etc]# df -h
Filesystem             Size  Used Avail Use% Mounted on
devtmpfs               4.0M     0  4.0M   0% /dev
tmpfs                  888M     0  888M   0% /dev/shm
tmpfs                  356M  5.1M  351M   2% /run
/dev/mapper/rhel-root   17G  2.2G   15G  13% /
/dev/sda1              960M  344M  617M  36% /boot
tmpfs                  178M     0  178M   0% /run/user/0
server30:/common        17G  2.2G   15G  13% /autoindir/sharenfs

Local File Systems and Swap

File Systems and File System Types

File systems

• Can be optimized, resized, mounted, and unmounted independently.
• Must be connected to the directory hierarchy in order to be accessed by users and applications.
• Mounting may be accomplished automatically at system boot or manually as required.
• Can be mounted or unmounted using their unique identifiers, labels, or device files.
• Each file system is created in a discrete partition, VDO volume, or logical volume.
• A typical production RHEL system usually has numerous file systems.
• During OS installation, only two file systems— / and /boot —are created in the default disk layout, but you can design a custom disk layout and construct separate containers to store dissimilar information.
• Typical additional file systems that may be created during an installation are /home, /opt, /tmp, /usr, and /var.
• / and /boot—are required for installation and booting.

Storing disparate data in distinct file systems versus storing all data in a single file system offers the following advantages:

• Make any file system accessible (mount) or inaccessible (unmount) to users independent of other file systems. This hides or reveals information contained in that file system.
• Perform file system repair activities on individual file systems
• Keep dissimilar data in separate file systems
• Optimize or tune each file system independently
• Grow or shrink a file system independent of other file systems

3 types of file systems:

• disk-based, network-based, and memory-based.

Disk-based

• Typically created on physical drives using SATA, USB, Fibre Channel, and other technologies.
• store information persistently

Network-based

• Essentially disk-based file systems shared over the network for remote access.
• store information persistently

Memory-based

• Virtual
• Created at system startup and destroyed when the system goes down.
• data saved in virtual file systems does not survive across system reboots.

Ext3

• Disk based
• The third generation of the extended filesystem.
• Metadata journaling for faster recovery
• Superior reliability
• Creation of up to 32,000 subdirectories
• supports larger file systems and bigger files than its predecessor

Ext4

• Disk based
• Successor to Ext3.
  • Supports all features of Ext3 in addition to:
    • Larger file system size
    • Bigger file size
    • Unlimited number of subdirectories
    • Metadata and quota journaling
    • Extended user attributes

XFS

• Disk based
• Highly scalable and high-performing 64-bit file system.
• Supports:
  • Metadata journaling for faster crash recovery
  • Online defragmentation, expansion, quota journaling, and extended user attributes
• default file system type in RHEL 9.

VFAT

• Disk based
• Used for post-Windows 95 file system formats on hard disks, USB drives, and floppy disks.

ISO9660

• Disk based
• Used for optical file systems such as CD and DVD.

NFS - (Network File System.)

• Network based
• Shared directory or file system for remote access by other Linux systems.

AutoFS (Auto File System)

• Network based
• NFS file system set to mount and unmount automatically on remote client systems.

Extended File Systems

• First generation is obsolete and is no longer supported
• Second, third, and fourth generations are currently available and supported.
• Fourth generation is the latest in the series and is superior in features and enhancements to its predecessors.
• Structure is built on a partition or logical volume at the time of file system creation.
• Structure is divided into two sets:
  • first set holds the file system’s metadata and it is very tiny.
    • Superblock
      • keeps vital file system structural information:
        • type
        • size
        • status of the file system
        • number of data blocks it contains
        • automatically replicated and maintained at various known locations throughout the file system.
        • primary superblock
          • superblock at the beginning of the file system
        • backup superblocks.
          • I used to supplant the corrupted or lost primary superblock to bring the file system back to its normal state.
          • Copy of the primary
    • Inode table
      • maintains a list of index node (inode) numbers.
      • Each file is assigned an inode number at the time of its creation, and the inode number
        • holds the file’s attributes such as:
          • type
          • permissions
          • ownership
          • owning group
          • size
          • last access/modification time
          • holds and keeps track of the pointers to the actual data blocks where the file contents are located.
  • second set stores the actual data, and it occupies almost the entire partition or the logical volume (VDO and LVM) space.\

journaling

• Supported by Ext3 and Ext4

• Recover swiftly after a system crash.

• keep track of recent changes in their metadata in a journal (or log).

• Each metadata update is written in its entirety to the journal after completion.

• The system peruses the journal of each extended file system following the reboot after a crash to determine if there are any errors

• Lets the system recover the file system rapidly using the latest metadata information stored in its journal.

• Ext3 that supports file systems up to 16TiB and files up to 2TiB,

• Ext4 supports very large file systems up to 1EiB (ExbiByte) and files up to 16TiB (TebiByte).

  • Uses a series of contiguous physical blocks on the hard disk called extents, resulting in improved read and write performance with reduced fragmentation.
  • Supports extended user attributes, metadata and quota journaling, etc.

XFS File System

• High-performing 64-bit extent-based journaling file system type.
• Allows the creation of file systems and files up to 8EiB (ExbiByte).
• Does not run file system checks at system boot
• Relies on you to use the xfs_repair utility to manually fix any issues.
• Sets the extended user attributes and certain mount options by default on new file systems.
• Enables defragmentation on mounted and active file systems to keep as much data in contiguous blocks as possible for faster access.
• Inability to shrink.
• Uses journaling for metadata operations, guaranteeing the consistency of the file system against abnormal or forced unmounting.
• Journal information is read and any pending metadata transactions are replayed when the XFS file system is remounted.
• Speedy input/output performance.
• Can be snapshot in a mounted, active state.

VFAT File System

• Extension to the legacy FAT file system (FAT16)
• Supports 255 characters in filenames including spaces and periods
• Does not differentiate between lowercase and uppercase letters.
• Primarily used on removable media, such as floppy and USB flash drives, for exchanging data between Linux and Windows.

ISO9660 File System

• For removable optical disc media such as CD/DVD drives

File System Management

File System Administration Commands

• Some are limited to their operations on the Extended, XFS, or VFAT file system type.
• Others are general and applicable to all file system types.

Extended File System Management Commands

e2label

• Modifies the label of a file system

tune2fs

• Tunes or displays file system attributes

XFS Management Commands

xfs_admin

• Tunes file system attributes

xfs_growfs

• Extends the size of a file system

xfs_info

• Exhibits information about a file system

General File System Commands

blkid

• Displays block device attributes including their UUIDs and labels

df

• Reports file system utilization

du

• Calculates disk usage of directories and file systems

fsadm

• Resizes a file system. This command is automatically invoked when the lvresize command is run with the -r switch.

lsblk

• Lists block devices and file systems and their attributes including their UUIDs and labels

mkfs

• Creates a file system. Use the -t option and specify ext3, ext4, vfat, or xfs file system type.

mount

• Mount a file system for user access.
• Display currently mounted file systems.

umount

• Unmount a file system.

Mounting and Unmounting File Systems

• File system must be connected to the directory structure at a desired attachment point, (mount point)
• A mount point in essence is any empty directory that is created and used for this purpose.

Use the mount command to view information about xfs mounted file systems:

[root@server2 ~]# mount -t xfs
/dev/mapper/rhel-root on / type xfs (rw,relatime,seclabel,attr2,inode64,logbufs=8,logbsize=32k,noquota)
/dev/sda1 on /boot type xfs (rw,relatime,seclabel,attr2,inode64,logbufs=8,logbsize=32k,noquota)

Mount command

• -t option
  • type.
• Mount a file system to a mount point.
• Performed with the root user privileges.
• Requires the absolute pathnames of the file system block device and the mount point name.
• Accepts the UUID or label of the file system in lieu of the block device name.
• Mount all or a specific type of file system.
• Upon successful mount, the kernel places an entry for the file system in the /proc/self/mounts file.
• A mount point should be empty when an attempt is made to mount a file system on it, otherwise the content of the mount point will hide.
• The mount point must not be in use or the mount attempt will fail.

auto (noauto)

• Mounts (does not mount) the file system when the -a option is specified

defaults

• Mounts a file system with all the default values (async, auto, rw, etc.)

_netdev

• Used for a file system that requires network connectivity in place before it can be mounted. NFS is an example.

remount

• Remounts an already mounted file system to enable or disable an option

ro (rw)

• Mounts a file system read-only read/write)

umount Command

• Detach a file system from the directory hierarchy and make it inaccessible to users and applications.
• Expects the absolute pathname to the block device containing the file system or its mount point name in order to detach it.
• Unmount all or a specific type of file system.
• Kernel removes the corresponding file system entry from the /proc/self/mounts file after it has been successfully disconnected.

Determining the UUID of a File System

• Extended and XFS file systems have a 128-bit (32 hexadecimal characters) UUID (Universally Unique IDentifier) assigned to it at the time of its creation.

• UUIDs assigned to vfat file systems are 32-bit (8 hexadecimal characters) in length.

• Assigning a UUID makes the file system unique among many other file systems that potentially exist on the system.

• Persistent across system reboots.

• Used by default in RHEL 9 in the /etc/fstab file for any file system that is created by the system in a standard partition.

• RHEL attempts to mount all file systems listed in the /etc/fstab file at reboots.

• Each file system has an associated device file and UUID, but may or may not have a corresponding label.

• The system checks for the presence of each file system’s device file, UUID, or label, and then attempts to mount it.

Determine the UUID of /boot

[root@server2 ~]# lsblk | grep boot
├─sda1          8:1    0    1G  0 part /boot

[root@server2 ~]# sudo xfs_admin -u /dev/sda1
UUID = 630568e1-608f-4603-9b97-e27f82c7d4b4

[root@server2 ~]# sudo blkid /dev/sda1
/dev/sda1: UUID="630568e1-608f-4603-9b97-e27f82c7d4b4" TYPE="xfs" PARTUUID="7dcb43e4-01"

[root@server2 ~]# sudo lsblk -f /dev/sda1
NAME FSTYPE FSVER LABEL UUID                                 FSAVAIL FSUSE% MOUNTPOINTS
sda1 xfs                630568e1-608f-4603-9b97-e27f82c7d4b4  616.1M    36% /boot

For extended file systems, you can use the tune2fs, blkid, or lsblk commands to determine the UUID.

A UUID is also assigned to a file system that is created in a VDO or LVM volume; however, it need not be used in the fstab file, as the device files associated with the logical volumes are always unique and persistent.

Labeling a File System

• A unique label may be used instead of a UUID to keep the file system association with its device file exclusive and persistent across system reboots.
• A label is limited to a maximum of 12 characters on the XFS file system
• 16 characters on the Extended file system.
• By default, no labels are assigned to a file system at the time of its creation.

The /boot file system is located in the /dev/sda1 partition and its type is XFS. You can use the xfs_admin or the lsblk command as follows to determine its label:

[root@server2 ~]# sudo xfs_admin -l /dev/sda1
label = ""

[root@server2 ~]# sudo lsblk -f /dev/sda1
NAME FSTYPE FSVER LABEL UUID                                 FSAVAIL FSUSE% MOUNTPOINTS
sda1 xfs                630568e1-608f-4603-9b97-e27f82c7d4b4  616.1M    36% /boot

• Not needed on a file system if you intend to use its UUID or if it is created in a logical volume
• You can still apply one using the xfs_admin command with the -L option.
• Labeling an XFS file system requires that the target file system be unmounted.

unmount /boot, set the label “bootfs” on its device file, and remount it:

[root@server2 ~]# sudo umount /boot
[root@server2 ~]# sudo xfs_admin -L bootfs /dev/sda1
writing all SBs
new label = "bootfs"

Confirm the new label by executing sudo xfs_admin -l /dev/sda1 or sudo lsblk -f /dev/sda1.

For extended file systems, you can use the e2label command to apply a label and the tune2fs, blkid, and lsblk commands to view and verify.

Now you can replace the UUID=\"22d05484-6ae1-4ef8-a37d-abab674a5e35" for /boot in the fstab file with LABEL=bootfs, and unmount and remount /boot as demonstrated above for confirmation.

[root@server2 ~]# mount /boot
mount: (hint) your fstab has been modified, but systemd still uses
       the old version; use 'systemctl daemon-reload' to reload.

A label may also be applied to a file system created in a logical volume; however, it is not recommended for use in the fstab file, as the device files for logical volumes are always unique and remain persistent across system reboots.

Automatically Mounting a File System at Reboots

/etc/fstab

• File systems defined in the /etc/fstab file are mounted automatically at reboots.
• Must contain proper and complete information for each listed file system.
• An incomplete or inaccurate entry might leave the system in an undesirable or unbootable state.
• Only need to specify one of the four attributes
  • Block device name
  • UUID
  • label
  • mount point
• The mount command obtains the rest of the information from this file.
• Only need to specify one of these attributes with the umount command to detach it from the directory hierarchy.
• Contains entries for file systems that are created at the time of installation.

[root@server2 ~]# cat /etc/fstab

#
# /etc/fstab
# Created by anaconda on Sun Feb 25 12:11:47 2024
#
# Accessible filesystems, by reference, are maintained under '/dev/disk/'.
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info.
#
# After editing this file, run 'systemctl daemon-reload' to update systemd
# units generated from this file.
#
/dev/mapper/rhel-root   /                       xfs     defaults        0 0
LABEL=bootfs /boot                   xfs     defaults        0 0
/dev/mapper/rhel-swap   none                    swap    defaults        0 0

EXAM TIP: Any missing or invalid entry in this file may render the system unbootable. You will have to boot the system in emergency mode to fix this file. Ensure that you understand each field in the file for both file system and swap entries.

The format of this file is such that each row is broken out into six columns to identify the required attributes for each file system to be successfully mounted. Here is what the columns contain:

Column 1:

• physical or virtual device path where the file system is resident, or its associated UUID or label.
• can be entries for network file systems here as well.

Column 2:

• Identifies the mount point for the file system.
• swap partitions, use either “none” or “swap”.

Column 3:

• Type of file system such as Ext3, Ext4, XFS, VFAT, or ISO9660.
• For swap, the type “swap” is used.
• may use “auto” instead to leave it up to the mount command to determine the type of the file system.

Column 4:

• Identifies one or more comma-separated options to be used when mounting the file system.
• Consult the manual pages of the mount command or the fstab file for additional options and details.

Column 5:

• Used by the dump utility to ascertain the file systems that need to be dumped.
• Value of 0 (or the absence of this column) disables this check.
• This field is applicable only on Extended file systems;
• XFS does not use it.

Column 6:

• Sequence number in which to run the e2fsck (file system check and repair utility for Extended file system types) utility on the file system at system boot.

• By default, 0 is used for memory-based, remote, and removable file systems, 1 for /, and 2 for /boot and other physical file systems. 0 can also be used for /, /boot, and other physical file systems you don’t want to be checked or repaired.

• Applicable only on Extended file systems;

• XFS does not use it.

• 0 in columns 5 and 6 for XFS, virtual, remote, and removable file system types has no meaning. You do not need to add them for these file system types.

Lab: Create and Mount Ext4, VFAT, and XFS File Systems in Partitions (server2)

• Create 2 x 100MB partitions on the /dev/sdb disk,
• initialize them separately with the Ext4 and VFAT file system types,
• define them for persistence using their UUIDs,
• create mount points called /ext4fs1 and /vfatfs1,
• attach them to the directorystructure
• verify their availability and usage
• you will use the disk /dev/sdc and repeat the above procedure to establish an XFS file system in it and mount it on /xfsfs1.

1. Apply the label “msdos” to the sdb disk using the parted command:

[root@server20 ~]# sudo parted /dev/sdb mklabel msdos
Warning: The existing disk label on /dev/sdb will be destroyed and all data on this disk will be
lost. Do you want to continue?
Yes/No? y                                                                 
Information: You may need to update /etc/fstab.

2. Create 2 x 100MB primary partitions on sdb with the parted command:

[root@server20 ~]# sudo parted /dev/sdb mkpart primary 1 101m
Information: You may need to update /etc/fstab.

[root@server20 ~]# sudo parted /dev/sdb mkpart primary 102 201m
Information: You may need to update /etc/fstab.

3. Initialize the first partition (sdb1) with Ext4 file system type using the mkfs command:

[root@server20 ~]# sudo mkfs -t ext4 /dev/sdb1
mke2fs 1.46.5 (30-Dec-2021)
/dev/sdb1 contains a LVM2_member file system
Proceed anyway? (y,N) y
Creating filesystem with 97280 1k blocks and 24288 inodes
Filesystem UUID: 73db0582-7183-42aa-951d-2f48b7712597
Superblock backups stored on blocks: 
	8193, 24577, 40961, 57345, 73729

Allocating group tables: done                            
Writing inode tables: done                            
Creating journal (4096 blocks): done
Writing superblocks and filesystem accounting information: done 

4. Initialize the second partition (sdb2) with VFAT file system type using the mkfs command:

[root@server20 ~]# sudo mkfs -t vfat /dev/sdb2
mkfs.fat 4.2 (2021-01-31)

5. Initialize the whole disk (sdc) with the XFS file system type using the mkfs.xfs command. Add the -f flag to force the removal of any old partitioning or labeling information from the disk.

[root@server20 ~]# sudo mkfs.xfs /dev/sdc -f 
Filesystem should be larger than 300MB.
Log size should be at least 64MB.
Support for filesystems like this one is deprecated and they will not be supported in future releases.
meta-data=/dev/sdc               isize=512    agcount=4, agsize=16000 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=1        finobt=1, sparse=1, rmapbt=0
         =                       reflink=1    bigtime=1 inobtcount=1 nrext64=0
data     =                       bsize=4096   blocks=64000, imaxpct=25
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0, ftype=1
log      =internal log           bsize=4096   blocks=1368, version=2
         =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0

6. Determine the UUIDs for all three file systems using the lsblk command:

[root@server2 ~]# lsblk -f /dev/sdb /dev/sdc
NAME   FSTYPE FSVER LABEL UUID                                 FSAVAIL FSUSE% MOUNTPOINTS
sdb                                                                           
├─sdb1 ext4   1.0         0bdd22d0-db53-40bb-8cc7-36efc9184196                
└─sdb2 vfat   FAT16       FB3A-6572                                           
sdc    xfs                91884326-9686-4569-96fa-9adb02c1f6f4>)

7. Open the /etc/fstab file, go to the end of the file, and append entries for the file systems for persistence using their UUIDs:

UUID=0bdd22d0-db53-40bb-8cc7-36efc9184196 /ext4fs1 ext4 defaults 0 0                
UUID=FB3A-6572 /vfatfs1 vfat defaults 0 0                                          
UUID=91884326-9686-4569-96fa-9adb02c1f6f4 /xfsfs1 xfs defaults 0 0

8. Create mount points /ext4fs1, /vfatfs1, and /xfsfs1 for the three file systems using the mkdir command: [root@server2 ~]# sudo mkdir /ext4fs1 /vfatfs1 /xfsfs1

9. Mount the new file systems using the mount command. This command will fail if there are any invalid or missing information in the file.

[root@server2 ~]# sudo mount -a
mount: (hint) your fstab has been modified, but systemd still uses
       the old version; use 'systemctl daemon-reload' to reload.

10. View the mount and availability status as well as the types of all three file systems using the df command:

[root@server2 ~]# df -hT
Filesystem            Type      Size  Used Avail Use% Mounted on
devtmpfs              devtmpfs  4.0M     0  4.0M   0% /dev
tmpfs                 tmpfs     888M     0  888M   0% /dev/shm
tmpfs                 tmpfs     356M  5.1M  351M   2% /run
/dev/mapper/rhel-root xfs        17G  2.0G   15G  12% /
/dev/sda1             xfs       960M  344M  617M  36% /boot
tmpfs                 tmpfs     178M     0  178M   0% /run/user/0
/dev/sdb1             ext4       84M   14K   77M   1% /ext4fs1
/dev/sdb2             vfat       95M     0   95M   0% /vfatfs1
/dev/sdc              xfs       245M   15M  231M   6% /xfsfs1

Lab: Create and Mount Ext4 and XFS File Systems in LVM Logical Volumes (server2)

• Create a volume group called vgfs comprised of a 172MB physical volume created in a partition on the /dev/sdd disk.
• The PE size for the volume group should be set at 16MB.
• Create two logical volumes called ext4vol and xfsvol of sizes 80MB each and initialize them with the Ext4 and XFS file system types.
• Ensure that both file systems are persistently defined using their logical volume device filenames.
• Create mount points called /ext4fs2 and /xfsfs2,
• Mount the file systems.
• Verify their availability and usage.

1. Create a 172MB partition on the sdd disk using the parted command:

[root@server2 ~]# sudo parted /dev/sdd mkpart pri 1 172m
Information: You may need to update /etc/fstab.

2. Initialize the sdd1 partition for use in LVM using the pvcreate command:

[root@server2 ~]# sudo pvcreate /dev/sdd1
  Device /dev/sdb2 has updated name (devices file /dev/sdd2)
  Device /dev/sdb1 has no PVID (devices file brKVLFEG3AoBzhWoso0Sa1gLYHgNZ4vL)
  Physical volume "/dev/sdd1" successfully created.

3. Create the volume group vgfs with a PE size of 16MB using the physical volume sdd1:

[root@server2 ~]# sudo vgcreate -s 16 vgfs /dev/sdd1
  Volume group "vgfs" successfully created

The PE size is not easy to alter after a volume group creation, so ensure it is defined as required at creation.

4. Create two logical volumes ext4vol and xfsvol of size 80MB each in vgfs using the lvcreate command:

[root@server2 ~]# sudo lvcreate -n ext4vol -L 80 vgfs
  Logical volume "ext4vol" created.
  
[root@server2 ~]# sudo lvcreate  -n xfsvol -L 80 vgfs
  Logical volume "xfsvol" created.

5. Format the ext4vol logical volume with the Ext4 file system type using the mkfs.ext4 command:

[root@server2 ~]# sudo mkfs.ext4 /dev/vgfs/ext4vol
mke2fs 1.46.5 (30-Dec-2021)
Creating filesystem with 81920 1k blocks and 20480 inodes
Filesystem UUID: 4ed1fef7-2164-485b-8035-7f627cd59419
Superblock backups stored on blocks: 
	8193, 24577, 40961, 57345, 73729

Allocating group tables: done                            
Writing inode tables: done                            
Creating journal (4096 blocks): done
Writing superblocks and filesystem accounting information: done

You can also use sudo mkfs -t ext4 /dev/vgfs/ext4vol.

6. Format the xfsvol logical volume with the XFS file system type using the mkfs.xfs command:

[root@server2 ~]# sudo mkfs.xfs /dev/vgfs/xfsvol
Filesystem should be larger than 300MB.
Log size should be at least 64MB.
Support for filesystems like this one is deprecated and they will not be supported in future releases.
meta-data=/dev/vgfs/xfsvol       isize=512    agcount=4, agsize=5120 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=1        finobt=1, sparse=1, rmapbt=0
         =                       reflink=1    bigtime=1 inobtcount=1 nrext64=0
data     =                       bsize=4096   blocks=20480, imaxpct=25
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0, ftype=1
log      =internal log           bsize=4096   blocks=1368, version=2
         =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0

You may also use sudo mkfs -t xfs /dev/vgfs/xfsvol instead.

7. Open the /etc/fstab file, go to the end of the file, and append entries for the file systems for persistence using their device files:

/dev/vgfs/ext4vol /ext4fs2 ext4 defaults 0 0
/dev/vgfs/xfsvol /xfsfs2 xfs defaults 0 0

8. Create mount points /ext4fs2 and /xfsfs2 using the mkdir command: [root@server2 ~]# sudo mkdir /ext4fs2 /xfsfs2

9. Mount the new file systems using the mount command. This command will fail if there is any invalid or missing information in the file.

[root@server2 ~]# sudo mount -a
mount: (hint) your fstab has been modified, but systemd still uses
       the old version; use 'systemctl daemon-reload' to reload.

10. View the mount and availability status as well as the types of the new LVM file systems using the lsblk and df commands:

[root@server2 ~]# lsblk /dev/sdd
NAME             MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
sdd                8:48   0  250M  0 disk 
└─sdd1             8:49   0  163M  0 part 
  ├─vgfs-ext4vol 253:2    0   80M  0 lvm  /ext4fs2
  └─vgfs-xfsvol  253:3    0   80M  0 lvm  /xfsfs2
[root@server2 ~]# df -hT | grep fs2
/dev/mapper/vgfs-ext4vol ext4       70M   14K   64M   1% /ext4fs2
/dev/mapper/vgfs-xfsvol  xfs        75M  4.8M   70M   7% /xfsfs2

Lab: Resize Ext4 and XFS File Systems in LVM Logical Volumes (server 2)

• Grow the size of the vgfs volume group that was created in the last lab by adding the whole sde disk to it.
• Extend the ext4vol logical volume along with the file system it contains by 40MB using two separate commands.
• Extend the xfsvol logical volume along with the file system it contains by 40MB using a single command.
• Verify the new extensions.

1. Initialize the sde disk and add it to the vgfs volume group:

sde had a gpt partition table with no partitions ran the following to reset it:

[root@server2 ~]# dd if=/dev/zero of=/dev/sde bs=1M count=2 conv=fsync
2+0 records in
2+0 records out
2097152 bytes (2.1 MB, 2.0 MiB) copied, 0.0102036 s, 206 MB/s
[root@server2 ~]# sudo partprobe /dev/sde
[root@server2 ~]# sudo pvcreate /dev/sde
  Physical volume "/dev/sde" successfully created.

[root@server2 ~]# sudo pvcreate /dev/sde
  Physical volume "/dev/sde" successfully created.
[root@server2 ~]# sudo vgextend vgfs /dev/sde
  Volume group "vgfs" successfully extended

2. Confirm the new size of vgfs using the vgs and vgdisplay commands:

[root@server2 ~]# sudo vgs
  VG   #PV #LV #SN Attr   VSize   VFree  
  rhel   1   2   0 wz--n- <19.00g      0 
  vgfs   2   2   0 wz--n- 400.00m 240.00m

[root@server2 ~]# vgdisplay vgfs
  Devices file sys_wwid t10.ATA_VBOX_HARDDISK_VBa5e3cbf7-10921e08 PVID qeP9dCevNnTy422I8p18NxDKQ2WyDodU last seen on /dev/sdf1 not found.
  --- Volume group ---
  VG Name               vgfs
  System ID             
  Format                lvm2
  Metadata Areas        2
  Metadata Sequence No  4
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                2
  Open LV               2
  Max PV                0
  Cur PV                2
  Act PV                2
  VG Size               400.00 MiB
  PE Size               16.00 MiB
  Total PE              25
  Alloc PE / Size       10 / 160.00 MiB
  Free  PE / Size       15 / 240.00 MiB
  VG UUID               amDADJ-I4dH-jQUF-RFcE-58iL-jItl-5ti6LS

There are now two physical volumes in the volume group and the total size increased to 400MiB.

3. Grow the logical volume ext4vol and the file system it holds by 40MB using the lvextend and fsadm command pair. Make sure to use an uppercase L to specify the size. The default unit is MiB. The plus sign (+) signifies an addition to the current size.

[root@server2 ~]# sudo lvextend -L +40 /dev/vgfs/ext4vol
  Rounding size to boundary between physical extents: 48.00 MiB.
  Size of logical volume vgfs/ext4vol changed from 80.00 MiB (5 extents) to 128.00 MiB (8 extents).
  Logical volume vgfs/ext4vol successfully resized.
  
[root@server2 ~]# sudo fsadm resize /dev/vgfs/ext4vol
resize2fs 1.46.5 (30-Dec-2021)
Filesystem at /dev/mapper/vgfs-ext4vol is mounted on /ext4fs2; on-line resizing required
old_desc_blocks = 1, new_desc_blocks = 1
The filesystem on /dev/mapper/vgfs-ext4vol is now 131072 (1k) blocks long.

The resize subcommand instructs the fsadm command to grow the file system to the full length of the specified logical volume.

4. Grow the logical volume xfsvol and the file system (-r) it holds by (+) 40MB using the lvresize command:

[root@server2 ~]# sudo lvresize -r -L +40 /dev/vgfs/xfsvol
  Rounding size to boundary between physical extents: 48.00 MiB.
  Size of logical volume vgfs/xfsvol changed from 80.00 MiB (5 extents) to 128.00 MiB (8 extents).
  File system xfs found on vgfs/xfsvol mounted at /xfsfs2.
  Extending file system xfs to 128.00 MiB (134217728 bytes) on vgfs/xfsvol...
xfs_growfs /dev/vgfs/xfsvol
meta-data=/dev/mapper/vgfs-xfsvol isize=512    agcount=4, agsize=5120 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=1        finobt=1, sparse=1, rmapbt=0
         =                       reflink=1    bigtime=1 inobtcount=1 nrext64=0
data     =                       bsize=4096   blocks=20480, imaxpct=25
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0, ftype=1
log      =internal log           bsize=4096   blocks=1368, version=2
         =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0
data blocks changed from 20480 to 32768
xfs_growfs done
  Extended file system xfs on vgfs/xfsvol.
  Logical volume vgfs/xfsvol successfully resized.

5. Verify the new extensions to both logical volumes using the lvs command. You may also issue the lvdisplay or vgdisplay command instead.

[root@server2 ~]# sudo lvs | grep vol
  Devices file sys_wwid t10.ATA_VBOX_HARDDISK_VBa5e3cbf7-10921e08 PVID qeP9dCevNnTy422I8p18NxDKQ2WyDodU last seen on /dev/sdf1 not found.
  ext4vol vgfs -wi-ao---- 128.00m                                                    
  xfsvol  vgfs -wi-ao---- 128.00m   

6. Check the new sizes and the current mount status for both file systems using the df and lsblk commands:

[root@server2 ~]# df -hT | grep -E 'ext4vol|xfsvol'
/dev/mapper/vgfs-xfsvol  xfs       123M  5.4M  118M   5% /xfsfs2
/dev/mapper/vgfs-ext4vol ext4      115M   14K  107M   1% /ext4fs2

[root@server2 ~]# lsblk /dev/sdd /dev/sde
NAME             MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
sdd                8:48   0  250M  0 disk 
└─sdd1             8:49   0  163M  0 part 
  ├─vgfs-ext4vol 253:2    0  128M  0 lvm  /ext4fs2
  └─vgfs-xfsvol  253:3    0  128M  0 lvm  /xfsfs2
sde                8:64   0  250M  0 disk 
├─vgfs-ext4vol   253:2    0  128M  0 lvm  /ext4fs2
└─vgfs-xfsvol    253:3    0  128M  0 lvm  /xfsfs2

Lab: Create and Mount XFS File System in LVM VDO Volume

• Create an LVM VDO volume called lvvdo of virtual size 20GB on the 5GB sdf disk in a volume group called vgvdo1.
• Initialize the volume with the XFS file system type.
• Define it for persistence using its device files.
• Create a mount point called /xfsvdo1, attach it to the directory structure.
• verify its availability and usage.\

1. Initialize the sdf disk using the pvcreate command:

[root@server2 ~]# sudo pvcreate /dev/sdf
  WARNING: adding device /dev/sdf with idname t10.ATA_VBOX_HARDDISK_VBa5e3cbf7-10921e08 which is already used for missing device.
  Physical volume "/dev/sdf" successfully created.

2. Create vgvdo1 volume group using the vgcreate command:

[root@server2 ~]# sudo vgcreate vgvdo1 /dev/sdf
  WARNING: adding device /dev/sdf with idname t10.ATA_VBOX_HARDDISK_VBa5e3cbf7-10921e08 which is already used for missing device.
  Volume group "vgvdo1" successfully created

3. Display basic information about the volume group:

root@server2 ~]# sudo vgdisplay vgvdo1
  Devices file sys_wwid t10.ATA_VBOX_HARDDISK_VBa5e3cbf7-10921e08 PVID qeP9dCevNnTy422I8p18NxDKQ2WyDodU last seen on /dev/sdf1 not found.
  --- Volume group ---
  VG Name               vgvdo1
  System ID             
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  1
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                0
  Open LV               0
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               <5.00 GiB
  PE Size               4.00 MiB
  Total PE              1279
  Alloc PE / Size       0 / 0   
  Free  PE / Size       1279 / <5.00 GiB
  VG UUID               b9u8Ng-m3BF-Jz2b-sBu8-gEG1-bBGQ-sBgrt0

4. Create a VDO volume called lvvdo1 using the lvcreate command. Use the -l option to specify the number of logical extents (1279) to be allocated and the -V option for the amount of virtual space (20GB).

[root@server2 ~]# sudo lvcreate -n lvvdo -l 1279 -V 20G --type vdo vgvdo1
WARNING: vdo signature detected on /dev/vgvdo1/vpool0 at offset 0. Wipe it? [y/n]: y
  Wiping vdo signature on /dev/vgvdo1/vpool0.
    The VDO volume can address 2 GB in 1 data slab.
    It can grow to address at most 16 TB of physical storage in 8192 slabs.
    If a larger maximum size might be needed, use bigger slabs.
  Logical volume "lvvdo" created.

5. Display detailed information about the volume group including the logical volume and the physical volume:

[root@server2 ~]# sudo vgdisplay -v vgvdo1
  Devices file sys_wwid t10.ATA_VBOX_HARDDISK_VBa5e3cbf7-10921e08 PVID qeP9dCevNnTy422I8p18NxDKQ2WyDodU last seen on /dev/sdf1 not found.
  --- Volume group ---
  VG Name               vgvdo1
  System ID             
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  3
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                2
  Open LV               0
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               <5.00 GiB
  PE Size               4.00 MiB
  Total PE              1279
  Alloc PE / Size       1279 / <5.00 GiB
  Free  PE / Size       0 / 0   
  VG UUID               b9u8Ng-m3BF-Jz2b-sBu8-gEG1-bBGQ-sBgrt0
   
  --- Logical volume ---
  LV Path                /dev/vgvdo1/vpool0
  LV Name                vpool0
  VG Name                vgvdo1
  LV UUID                nTPKtv-3yTW-J7Cy-HVP1-Aujs-cXZ6-gdS2fI
  LV Write Access        read/write
  LV Creation host, time server2, 2024-07-01 12:57:56 -0700
  LV VDO Pool data       vpool0_vdata
  LV VDO Pool usage      60.00%
  LV VDO Pool saving     100.00%
  LV VDO Operating mode  normal
  LV VDO Index state     online
  LV VDO Compression st  online
  LV VDO Used size       <3.00 GiB
  LV Status              NOT available
  LV Size                <5.00 GiB
  Current LE             1279
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
   
  --- Logical volume ---
  LV Path                /dev/vgvdo1/lvvdo
  LV Name                lvvdo
  VG Name                vgvdo1
  LV UUID                Z09BdK-ETJk-Gi53-m8Cg-mnTd-RYug-Z9nV0L
  LV Write Access        read/write
  LV Creation host, time server2, 2024-07-01 12:58:02 -0700
  LV VDO Pool name       vpool0
  LV Status              available
  # open                 0
  LV Size                20.00 GiB
  Current LE             5120
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:6
   
  --- Physical volumes ---
  PV Name               /dev/sdf     
  PV UUID               WKc956-Xp66-L8v9-VA6S-KWM5-5e3X-kx1v0V
  PV Status             allocatable
  Total PE / Free PE    1279 / 0

6. Display the new VDO volume creation using the lsblk command:

[root@server2 ~]# sudo lsblk /dev/sdf
NAME                    MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS
sdf                       8:80   0   5G  0 disk 
└─vgvdo1-vpool0_vdata   253:4    0   5G  0 lvm  
  └─vgvdo1-vpool0-vpool 253:5    0  20G  0 lvm  
    └─vgvdo1-lvvdo      253:6    0  20G  0 lvm  

The output shows the virtual volume size (20GB) and the underlying disk size (5GB).

7. Initialize the VDO volume with the XFS file system type using the mkfs.xfs command. The VDO volume device file is /dev/mapper/vgvdo1-lvvdo as indicated in the above output. Add the -f flag to force the removal of any old partitioning or labeling information from the disk.

[root@server2 mapper]# sudo mkfs.xfs /dev/mapper/vgvdo1-lvvdo
meta-data=/dev/mapper/vgvdo1-lvvdo isize=512    agcount=4, agsize=1310720 blks
         =                       sectsz=4096  attr=2, projid32bit=1
         =                       crc=1        finobt=1, sparse=1, rmapbt=0
         =                       reflink=1    bigtime=1 inobtcount=1 nrext64=0
data     =                       bsize=4096   blocks=5242880, imaxpct=25
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0, ftype=1
log      =internal log           bsize=4096   blocks=16384, version=2
         =                       sectsz=4096  sunit=1 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0
Discarding blocks...Done.

(lab said vgvdo1-lvvdo1 but it didn’t exist for me.)

8. Open the /etc/fstab file, go to the end of the file, and append the following entry for the file system for persistent mounts using its device file:

/dev/mapper/vgvdo1-lvvdo /xfsvdo1 xfs defaults 0 0 

9. Create the mount point /xfsvdo1 using the mkdir command:

[root@server2 mapper]# sudo mkdir /xfsvdo1

10. Mount the new file system using the mount command. This command will fail if there are any invalid or missing information in the file.

[root@server2 mapper]# sudo mount -a
mount: (hint) your fstab has been modified, but systemd still uses
       the old version; use 'systemctl daemon-reload' to reload.

The mount command with the -a flag is a validation test for the fstab file. It should always be executed after updating this file and before rebooting the server to avoid landing the system in an unbootable state.

11. View the mount and availability status as well as the type of the VDO file system using the lsblk and df commands:

[root@server2 mapper]# lsblk /dev/sdf
NAME                    MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS
sdf                       8:80   0   5G  0 disk 
└─vgvdo1-vpool0_vdata   253:4    0   5G  0 lvm  
  └─vgvdo1-vpool0-vpool 253:5    0  20G  0 lvm  
    └─vgvdo1-lvvdo      253:6    0  20G  0 lvm  /xfsvdo1

[root@server2 mapper]# df -hT /xfsvdo1
Filesystem               Type  Size  Used Avail Use% Mounted on
/dev/mapper/vgvdo1-lvvdo xfs    20G  175M   20G   1% /xfsvdo1

Monitoring File System Usage

df (disk free) command

• reports usage details for mounted file systems.
• reports the numbers in KBs unless the -m or -h option is specified to view the sizes in MBs or human-readable format.

Let’s run this command with the -h option on server2:

[root@server2 ~]# df -h
Filesystem             Size  Used Avail Use% Mounted on
devtmpfs               4.0M     0  4.0M   0% /dev
tmpfs                  888M     0  888M   0% /dev/shm
tmpfs                  356M  5.1M  351M   2% /run
/dev/mapper/rhel-root   17G  2.0G   15G  12% /
tmpfs                  178M     0  178M   0% /run/user/0
/dev/sda1              960M  344M  617M  36% /boot

Column 1:

• file system device file or type

Columns 2, 3, 4, 5, 6

• total, used, and available spaces in and the usage percentage and mount point

Useful flags

-T

• Add the file system type to the output (example: df -hT)

-x

• Exclude the specified file system type from the output (example: df -hx tmpfs)

-t

• Limit the output to a specific file system type (example: df -t xfs)

-i

• show inode information (example: df -hi)

Calculating Disk Usage

du command

• reports the amount of space a file or directory occupies.
• -m or -h option to view the output in MBs or human-readable format. In addition, you can
• view a usage summary with the -s switch and a grand total with -c.

Run this command on the /usr/bin directory to view the usage summary:

[root@server2 ~]# du -sh /usr/bin
151M	/usr/bin

Add a “total” row to the output and with numbers displayed in KBs:

[root@server2 ~]# du -sc /usr/bin
154444	/usr/bin
154444	total

[root@server2 ~]# du -sch /usr/bin
151M	/usr/bin
151M	total

Try this command with different options on the /usr/sbin/lvm file and observe the results.

Swap and its Management

• Move pages of idle data between physical memory and swap.

• Swap areas act as extensions to the physical memory.

• May be activated or deactivated independent of swap spaces located in other partitions and volumes.

• The system splits the physical memory into small logical chunks called pages and maps their physical locations to virtual locations on the swap to facilitate access by system processors.

• This physical-to-virtual mapping of pages is stored in a data structure called page table, and it is maintained by the kernel.

• When a program or process is spawned, it requires space in the physical memory to run and be processed.

• Although many programs can run concurrently, the physical memory cannot hold all of them at once.

• The kernel monitors the memory usage.

• As long as the free memory remains above a high threshold, nothing happens.

• When the free memory falls below that threshold, the system starts moving selected idle pages of data from physical memory to the swap space to make room to accommodate other programs.

• This piece in the process is referred to as page out.

• Since the system CPU performs the process execution in around-robin fashion, when the system needs this paged-out data for execution, the CPU looks for that data in the physical memory and a pagefault occurs, resulting in moving the pages back to the physical memory from the swap.

• This return of data to the physical memory is referred to as page in.

• The entire process of paging data out and in is known as demand paging.

• RHEL systems with less physical memory but high memory requirements can become over busy with paging out and in.

• When this happens, they do not have enough cycles to carry out other useful tasks, resulting in degraded system performance.

• The excessive amount of paging that affects the system performance is called thrashing.

• When thrashing begins, or when the free physical memory falls below a low threshold, the system deactivates idle processes and prevents new processes from being launched.

• The idle processes are only reactivated, and new processes are only allowed to be started when the system discovers that the available physical memory has climbed above the threshold level and thrashing has ceased.

Determining Current Swap Usage

• Size of a swap area should not be less than the amount of physical memory.
• Depending on workload requirements, it may be twice the size or larger.
• It is also not uncommon to see systems with less swap than the actual amount of physical memory.
• This is especially witnessed on systems with a huge physical memory size.

free command

• View memory and swap space utilization.
• view how much physical memory is installed (total), used (used), available (free), used by shared library routines (shared), holding data before it is written to disk (buffers), and used to store frequently accessed data (cached) on the system. The
• -h
  • list the values in human-readable format,
• -k
  • for KB,
• -m
  • for MB,
• -g
  • for GB,
• -t
  • display a line with the “total” at the bottom of the output.

[root@server2 mapper]# free -ht
               total        used        free      shared  buff/cache   available
Mem:           1.7Gi       783Mi       714Mi       5.0Mi       440Mi       991Mi
Swap:          2.0Gi          0B       2.0Gi
Total:         3.7Gi       783Mi       2.7Gi

Try free -hts 3 and free -htc 2 to refresh the output every three seconds (-s) and to display the output twice (-c).

• Reads memory and swap information from the /proc/meminfo file to produce the report. The values are shown in KBs by default, and they are slightly off from what is shown above with free. Here are the relevant fields from this file:

[root@server2 mapper]# cat /proc/meminfo | grep -E 'Mem|Swap'
MemTotal:        1818080 kB
MemFree:          731724 kB
MemAvailable:    1015336 kB
SwapCached:            0 kB
SwapTotal:       2097148 kB
SwapFree:        2097148 kB

Prioritizing Swap Spaces

• You may find multiple swap areas configured and activated to meet the workload demand.
• The default behavior of RHEL is to use the first activated swap area and move on to the next when the first one is exhausted.
• The system allows us to prioritize one area over the other by adding the option “pri” to the swap entries in the fstab file.
• This flag supports a value between -2 and 32767 with -2 being the default.
• A higher value of “pri” sets a higher priority for the corresponding swap region.
• For swap areas with an identical priority, the system alternates between them.

Swap Administration Commands

• In order to create and manage swap spaces on the system, the mkswap, swapon, and swapoff commands are available.
• Use mkswap to initialize a partition for use as a swap space.
• Once the swap area is ready, you can activate or deactivate it from the command line with the help of the other two commands,
• Can also set it up for automatic activation by placing an entry in the fstab file.
• The fstab file accepts the swap area’s device file, UUID, or label.

Lab: Create and Activate Swap in Partition and Logical Volume (server 2)

• Create one swap area in a new 40MB partition called sdb3 using the mkswap command.
• Create another swap area in a 140MB logical volume called swapvol in vgfs.
• Add their entries to the /etc/fstab file for persistence.
• Use the UUID and priority 1 for the partition swap and the device file and priority 2 for the logical volume swap.
• Activate them and use appropriate tools to validate the activation.

EXAM TIP: Use the lsblk command to determine available disk space.

1. Use parted print on the sdb disk and the vgs command on the vgfs volume group to determine available space for a new 40MB partition and a 144MB logical volume:

[root@server2 mapper]# sudo parted /dev/sdb print
Model: ATA VBOX HARDDISK (scsi)
Disk /dev/sdb: 262MB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags: 

Number  Start   End    Size    Type     File system  Flags
 1      1049kB  101MB  99.6MB  primary  ext4
 2      102MB   201MB  99.6MB  primary  fat16

[root@server2 mapper]# sudo vgs vgfs
  Devices file sys_wwid t10.ATA_VBOX_HARDDISK_VBa5e3cbf7-10921e08 PVID qeP9dCevNnTy422I8p18NxDKQ2WyDodU last seen on /dev/sdf1 not found.
  VG   #PV #LV #SN Attr   VSize   VFree  
  vgfs   2   2   0 wz--n- 400.00m 144.00m

The outputs show 49MB (250MB minus 201MB) free space on the sdb disk and 144MB free space in the volume group.

2. Create a partition called sdb3 of size 40MB using the parted command:

[root@server2 mapper]# sudo parted /dev/sdb mkpart primary 202 242
Information: You may need to update /etc/fstab.

3. Create logical volume swapvol of size 144MB in vgs using the lvcreate command:

[root@server2 mapper]# sudo lvcreate -L 144 -n swapvol vgfs               
  Logical volume "swapvol" created.

4. Construct swap structures in sdb3 and swapvol using the mkswap command:

[root@server2 mapper]# sudo mkswap /dev/sdb3
Setting up swapspace version 1, size = 38 MiB (39841792 bytes)
no label, UUID=a796e0df-b1c3-4c30-bdde-dd522bba4fff

[root@server2 mapper]# sudo mkswap /dev/vgfs/swapvol
Setting up swapspace version 1, size = 144 MiB (150990848 bytes)
no label, UUID=88196e73-feaf-4137-8743-f9340296aeec

5. Edit the fstab file and add entries for both swap areas for auto-activation on reboots. Obtain the UUID for partition swap with lsblk -f /dev/sdb3 and use the device file for logical volume. Specify their priorities.

UUID=a796e0df-b1c3-4c30-bdde-dd522bba4fff swap swap pri=1 0 0
/dev/vgfs/swapvol swap swap pri=2 0 0   

EXAM TIP: You will not be given any credit for this work if you forget to add entries to the fstab file.

6. Determine the current amount of swap space on the system using the swapon command:

[root@server2]# sudo swapon
NAME      TYPE      SIZE USED PRIO
/dev/dm-1 partition   2G   0B   -2

There is one 2GB swap area on the system and it is configured at the default priority of -2.

7. Activate the new swap regions using the swapon command:

[root@server2]# sudo swapon -a

8. Confirm the activation using the swapon command or by viewing the /proc/swaps file:

[root@server2 mapper]# sudo swapon
NAME      TYPE      SIZE USED PRIO
/dev/dm-1 partition   2G   0B   -2
/dev/sdb3 partition  38M   0B    1
/dev/dm-7 partition 144M   0B    2

[root@server2 mapper]# cat /proc/swaps
Filename				Type		Size		Used		Priority
/dev/dm-1                               partition	2097148		0		-2
/dev/sdb3                               partition	38908		0		1
/dev/dm-7                               partition	147452		0		2
#dm is device mapper

9. Issue the free command to view the reflection of swap numbers on the Swap and Total lines:

[root@server2 mapper]# free -ht
               total        used        free      shared  buff/cache   available
Mem:           1.7Gi       793Mi       706Mi       5.0Mi       438Mi       981Mi
Swap:          2.2Gi          0B       2.2Gi
Total:         3.9Gi       793Mi       2.9Gi

Local Filesystems and Swap DIY Labs

Lab: Create VFAT, Ext4, and XFS File Systems in Partitions and Mount Persistently

• Create three 70MB primary partitions on one of the available 250MB disks (lsblk) by invoking the parted utility directly at the command prompt.

[root@server2 mapper]# parted /dev/sdc mklabel msdos
Information: You may need to update /etc/fstab.

[root@server2 mapper]# parted /dev/sdc mkpart primary 1 70m
Information: You may need to update /etc/fstab.

root@server2 mapper]# parted /dev/sdb print
Model: ATA VBOX HARDDISK (scsi)
Disk /dev/sdb: 262MB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags: 

Number  Start   End     Size    Type     File system  Flags
 1      1049kB  70.3MB  69.2MB  primary

parted) mkpart primary 71MB 140MB                                    
Warning: The resulting partition is not properly aligned for best performance: 138671s % 2048s != 0s
Ignore/Cancel?                                                            
Ignore/Cancel? ignore                                                     
(parted) mkpart primary 140MB 210MB
Warning: The resulting partition is not properly aligned for best performance: 273438s % 2048s != 0s
Ignore/Cancel? ignore                                                     
(parted) print                                                            
Model: ATA VBOX HARDDISK (scsi)
Disk /dev/sdb: 262MB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags: 

Number  Start   End     Size    Type     File system  Flags
 1      1049kB  70.3MB  69.2MB  primary
 2      71.0MB  140MB   69.0MB  primary
 3      140MB   210MB   70.0MB  primary

• Apply label “msdos” if the disk is new.
• Initialize partition 1 with VFAT, partition 2 with Ext4, and partition 3 with XFS file system types.

[root@server2 mapper]# sudo mkfs -t vfat /dev/sdc1
mkfs.fat 4.2 (2021-01-31)

[root@server2 mapper]# sudo mkfs -t ext4 /dev/sdc2
mke2fs 1.46.5 (30-Dec-2021)
Creating filesystem with 67380 1k blocks and 16848 inodes
Filesystem UUID: 43b590ff-3330-4b88-aef9-c3a97d8cf51e
Superblock backups stored on blocks: 
	8193, 24577, 40961, 57345

Allocating group tables: done                            
Writing inode tables: done                            
Creating journal (4096 blocks): done
Writing superblocks and filesystem accounting information: done

[root@server2 mapper]# sudo mkfs -t xfs /dev/sdc3
Filesystem should be larger than 300MB.
Log size should be at least 64MB.
Support for filesystems like this one is deprecated and they will not be supported in future releases.
meta-data=/dev/sdb3              isize=512    agcount=4, agsize=4273 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=1        finobt=1, sparse=1, rmapbt=0
         =                       reflink=1    bigtime=1 inobtcount=1 nrext64=0
data     =                       bsize=4096   blocks=17089, imaxpct=25
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0, ftype=1
log      =internal log           bsize=4096   blocks=1368, version=2
         =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0

• Create mount points /vfatfs5, /ext4fs5, and /xfsfs5, and mount all three manually.

[root@server2 mapper]# mkdir /vfatfs5 /ext4fs5 /xfsfs5

[root@server2 mapper]# mount /dev/sdc1 /vfatfs5
mount: (hint) your fstab has been modified, but systemd still uses
       the old version; use 'systemctl daemon-reload' to reload.

[root@server2 mapper]# mount /dev/sdc2 /ext4fs5
mount: (hint) your fstab has been modified, but systemd still uses
       the old version; use 'systemctl daemon-reload' to reload.

[root@server2 mapper]# mount /dev/sdc3 /xfsfs5
mount: (hint) your fstab has been modified, but systemd still uses
       the old version; use 'systemctl daemon-reload' to reload.

[root@server2 mapper]# mount
/dev/sdb1 on /vfatfs5 type vfat (rw,relatime,fmask=0022,dmask=0022,codepage=437,iocharset=ascii,shortname=mixed,errors=remount-ro)
/dev/sdb2 on /ext4fs5 type ext4 (rw,relatime,seclabel)
/dev/sdb3 on /xfsfs5 type xfs (rw,relatime,seclabel,attr2,inode64,logbufs=8,logbsize=32k,noquota)

• Determine the UUIDs for the three file systems, and add them to the fstab file.

[root@server2 mapper]# blkid /dev/sdc1 /dev/sdc2 /dev/sdc3 >> /etc/fstab

[root@server2 mapper]# vim /etc/fstab

• Unmount all three file systems manually, and execute mount -a to mount them all. umount /dev/sdb1 /dev/sdb2 /dev/sdb3
• Run df -h for verification.

Lab: Create XFS File System in LVM VDO Volume and Mount Persistently

• Ensure that VDO software is installed. sudo dnf install kmod-kvdo

• Create a volume vdo5 with a logical size 20GB on a 5GB disk (lsblk) using the lvcreate command.

[root@server2 ~]# sudo lvcreate -n vdo5 -l 1279 -V 20G --type vdo vgvdo1
WARNING: vdo signature detected on /dev/vgvdo1/vpool0 at offset 0. Wipe it? [y/n]: y
  Wiping vdo signature on /dev/vgvdo1/vpool0.
    The VDO volume can address 2 GB in 1 data slab.
    It can grow to address at most 16 TB of physical storage in 8192 slabs.
    If a larger maximum size might be needed, use bigger slabs.
  Logical volume "vdo5" created.

• Initialize the volume with XFS file system type.

[root@server2 mapper]# sudo mkfs.xfs /dev/mapper/vgvdo1-vdo5
meta-data=/dev/mapper/vgvdo1-vdo5 isize=512    agcount=4, agsize=1310720 blks
         =                       sectsz=4096  attr=2, projid32bit=1
         =                       crc=1        finobt=1, sparse=1, rmapbt=0
         =                       reflink=1    bigtime=1 inobtcount=1 nrext64=0
data     =                       bsize=4096   blocks=5242880, imaxpct=25
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0, ftype=1
log      =internal log           bsize=4096   blocks=16384, version=2
         =                       sectsz=4096  sunit=1 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0
Discarding blocks...Done.

• Create mount point /vdofs5, and mount it manually.

[root@server2 mapper]# mkdir /vdofs5
[root@server2 mapper]#mount /dev/mapper/vgvdo1-vdo5 /vdofs5)/etc/fstab
[root@server2 mapper]# umount /dev/mapper/vgvdo1-vdo5

• Unmount the file system manually and execute mount -a to mount it back.

[root@server2 mapper]# blkid /dev/mapper/vgvdo1-vdo5 >> /etc/fstab
[root@server2 mapper]# vim /etc/fstab

• Run df -h to confirm.

Lab: Create Ext4 and XFS File Systems in LVM Volumes and Mount Persistently

• Initialize an available 250MB disk for use in LVM (lsblk).

[root@server2 mapper]# parted /dev/sdc mklabel msdos
Warning: The existing disk label on /dev/sdc will be destroyed and all data on
this disk will be lost. Do you want to continue?
Yes/No? y                                                                 
Information: You may need to update /etc/fstab.

[root@server2 mapper]# parted /dev/sdc mkpart primary 1 100%
Information: You may need to update /etc/fstab.

• Create volume group vg with PE size 8MB and add the physical volume.

[root@server2 ~]# sudo pvcreate /dev/sdc1
  Devices file /dev/sdc is excluded: device is partitioned.
  WARNING: adding device /dev/sdc1 with idname t10.ATA_VBOX_HARDDISK_VB6894bac4-590d5546 which is already used for /dev/sdc.
  Physical volume "/dev/sdc1" successfully created.
  
[root@server2 ~]# vgcreate -s 8 vg /dev/sdc1
  Devices file /dev/sdc is excluded: device is partitioned.
  WARNING: adding device /dev/sdc1 with idname t10.ATA_VBOX_HARDDISK_VB6894bac4-590d5546 which is already used for /dev/sdc.
  Volume group "vg" successfully created

• Create two logical volumes lv200 and lv300 of sizes 120MB and 100MB.

[root@server2 ~]# lvcreate -n lv200 -L 120 vg
  Devices file /dev/sdc is excluded: device is partitioned.
  Logical volume "lv200" created.
  
[root@server2 ~]# lvcreate -n lv300 -L 100 vg
  Rounding up size to full physical extent 104.00 MiB
  Logical volume "lv300" created.

• Use the vgs, pvs, lvs, and vgdisplay commands for verification.
• Initialize the volumes with Ext4 and XFS file system types.

[root@server2 ~]# mkfs.ext4 /dev/vg/lv200
mke2fs 1.46.5 (30-Dec-2021)
Creating filesystem with 122880 1k blocks and 30720 inodes
Filesystem UUID: 52eac2ee-b5bd-4025-9e40-356b38d21996
Superblock backups stored on blocks: 
	8193, 24577, 40961, 57345, 73729

Allocating group tables: done                            
Writing inode tables: done                            
Creating journal (4096 blocks): done
Writing superblocks and filesystem accounting information: done 

[root@server2 ~]# mkfs.xfs /dev/vg/lv300
Filesystem should be larger than 300MB.
Log size should be at least 64MB.
Support for filesystems like this one is deprecated and they will not be supported in future releases.
meta-data=/dev/vg/lv300          isize=512    agcount=4, agsize=6656 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=1        finobt=1, sparse=1, rmapbt=0
         =                       reflink=1    bigtime=1 inobtcount=1 nrext64=0
data     =                       bsize=4096   blocks=26624, imaxpct=25
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0, ftype=1
log      =internal log           bsize=4096   blocks=1368, version=2
         =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0

• Create mount points /lvmfs5 and /lvmfs6, and mount them manually.

[root@server2 ~]# mkdir /lvmfs5 /lvmfs6
[root@server2 ~]# mount /dev/vg/lv200 /lvmfs5
mount: (hint) your fstab has been modified, but systemd still uses
       the old version; use 'systemctl daemon-reload' to reload.
[root@server2 ~]# mount /dev/vg/lv300 /lvmfs6
mount: (hint) your fstab has been modified, but systemd still uses
       the old version; use 'systemctl daemon-reload' to reload.

• Add the file system information to the fstab file using their device files.

[root@server2 ~]# blkid /dev/vg/lv200 >> /etc/fstab
[root@server2 ~]# blkid /dev/vg/lv300 >> /etc/fstab
[root@server2 ~]# vim /etc/fstab

• Unmount the file systems manually, and execute mount -a to mount them back. Run df -h to confirm.

[root@server2 ~]# umount /dev/vg/lv200 /dev/vg/lv300
[root@server2 ~]# mount -a

Lab 14-4: Extend Ext4 and XFS File Systems in LVM Volumes

• initialize an available 250MB disk for use in LVM (lsblk).

[root@server2 ~]# pvcreate /dev/sdb
  Devices file /dev/sdc is excluded: device is partitioned.
WARNING: dos signature detected on /dev/sdb at offset 510. Wipe it? [y/n]: y
  Wiping dos signature on /dev/sdb.
  WARNING: adding device /dev/sdb with idname t10.ATA_VBOX_HARDDISK_VB428913dd-446a194f which is already used for missing device.
  Physical volume "/dev/sdb" successfully created.

• Add the new physical volume to volume group vg200.

[root@server2 ~]# vgextend vg /dev/sdb
  Devices file /dev/sdc is excluded: device is partitioned.
  WARNING: adding device /dev/sdb with idname t10.ATA_VBOX_HARDDISK_VB428913dd-446a194f which is already used for missing device.
  Volume group "vg" successfully extended

• Expand logical volumes lv200 and lv300 along with the underlying file systems to 200MB and 250MB.

[root@server2 ~]# lvextend -L 200m /dev/vg/lv200
  Size of logical volume vg/lv200 changed from 120.00 MiB (15 extents) to 200.00 MiB (25 extents).
  Logical volume vg/lv200 successfully resized.
[root@server2 ~]# lvextend -L 250m /dev/vg/lv200
  Rounding size to boundary between physical extents: 256.00 MiB.
  Size of logical volume vg/lv200 changed from 200.00 MiB (25 extents) to 256.00 MiB (32 extents).
  Logical volume vg/lv200 successfully resized.

• Use the vgs, pvs, lvs, vgdisplay, and df commands for verification.

Lab 14-5: Create Swap in Partition and LVM Volume and Activate Persistently

• Create two 100MB partitions on an available 250MB disk (lsblk) by invoking the parted utility directly at the command prompt.
• Apply label “msdos” if the disk is new.

[root@localhost ~]# parted /dev/sdd mklabel msdos
Information: You may need to update /etc/fstab.

[root@localhost ~]# parted /dev/sdd mkpart primary 1 100MB
Information: You may need to update /etc/fstab.

[root@localhost ~]# parted /dev/sdd mkpart primary 101 201
Information: You may need to update /etc/fstab.

• Initialize one of the partitions with swap structures.

[root@localhost ~]# sudo mkswap /dev/sdd1
Setting up swapspace version 1, size = 94 MiB (98562048 bytes)
no label, UUID=40eea6c2-b80c-4b25-ad76-611071db52d5

• Apply label swappart to the swap partition, and add it to the fstab file.

[root@localhost ~]# swaplabel -L swappart /dev/sdd1
[root@localhost ~]# blkid /dev/sdd1 >> /etc/fstab
[root@localhost ~]# vim /etc/fstab
UUID="40eea6c2-b80c-4b25-ad76-611071db52d5" swap swap pri=1 0 0

• Execute swapon -a to activate it.

• Run swapon -s to confirm activation.

• Initialize the other partition for use in LVM.

[root@localhost ~]# pvcreate /dev/sdd2
  Physical volume "/dev/sdd2" successfully created.

• Expand volume group vg (Lab 14-3) by adding this physical volume to it.

[root@localhost ~]# vgextend vg /dev/sdd2
  Volume group "vg200" successfully extended

• Create logical volume swapvol of size 180MB.

[root@localhost ~]# lvcreate -L 180 -n swapvol vg
  Logical volume "swapvol" created.

• Use the vgs, pvs, lvs, and vgdisplay commands for verification.
• Initialize the logical volume for swap.

[root@localhost vg200]# mkswap /dev/vg/swapvol
Setting up swapspace version 1, size = 180 MiB (188739584 bytes)
no label, UUID=a4b939d0-4b53-4e73-bee5-4c402aff6f9b

• Add an entry to the fstab file for the new swap area using its device file.

[root@localhost vg200]# vim /etc/fstab
/dev/vg200/swapvol swap swap pri=2 0 0

• Execute swapon -a to activate it.
• Run swapon -s to confirm activation.

Network File System (NFS)

NFS Basics and Configuration

Same tools for mounting and unmounting a filesystem.

• Mounted and accessed the same way as local filesystems.
• Network protocol that allows file sharing over the network.
• Multi-platform
• Multiple clients can access a single share at the same time.
• Reduced overhead and storage cost.
• Give users access to uniform data.
• Consolidate scattered user home directories.
• May cause client to hang if share is not accessible.
• Share stays mounted until manually unmounted or the client shuts down.
• Does not support wildcard characters or environment variables.

NFS Supported versions

• RHEL 9 Supports versions 3,4.0,4.1, and 4.2 (default)
• NFSv3 supports:
  • TCP and UDP.
  • asynchronous writes.
  • 64-bit files sizes.
  • Access files larger than 2GB.
• NFSv4.x supports:
  • All features of NFSv3.
  • Transit firewalls and work on internet.
  • Enhanced security and support for encrypted transfers and ACLs.
  • Better scalability
  • Better cross-platform
  • Better system crash handling
  • Use usernames and group names rather than UID and GID.
  • Uses TCP by default.
  • Can use UDP for backwards compatibility.
  • Version 4.2 only supports TCP

Network File System service

• Export shares to mount on remote clients
• Exporting
  • When the NFS server makes shares available.
• Mounting
  • When a client mounts an exported share locally.
  • Mount point should be empty before trying to mount a share on it.
• System can be both client and server.
• Entire directory tree of the share is shared.
• Cannot re-share a subdirectory of a share.
• A mounted share cannot be exported from the client.
• A single exported share is mounted on a directory mount point.
• Make sure to update the fstab file on the client.

NFS Server and Client Configuration

How to export a share

• Add entry of the share to /etc/exports using exportfs command
• Add firewall rule to allow access

Mount a share from the client side

• Use mount and add the filesystem to the fstab file.

Lab: Export Share on NFS Server

1. Install nfs-utils

 sudo dnf -y install nfs-utils

1. Create /common

 sudo mkdir /common

1. Add full permissions

 sudo chmod 777 /common

1. Add NFS service persistently to the firewalld configuration to allow NFS traffic and load the new rule:

sudo firewall-cmd --permanent --add-service nfs
sudo firewall-cmd --reload

1. Start the NFS service and enable it to autostart at system reboots:

sudo systemctl --now enable nfs-server

1. Verify Operational Status of the NFS services:

sudo systemctl status nfs-server

1. Open /etc/exports and add entry for /common to export it to server10 with read/write:

/common server10(rw)

1. Export the entry defined in /etc/exports/. -a option exports all entries in the file. -v is verbose.

sudo exportfs -av

1. Unexport the share (-u):

sudo exportfs -u server10:/common

1. Re-export the share:

sudo exportfs -av

LAB: Mount share on NFS client

1. Install nfs-utils

sudo dnf -y install nfs-utils

1. Create /local mount point

sudo mkdir /local

1. Mount the share manually:

sudo mount server20:/common /local

1. Confirm using mount: (shows nfs version)

mount | grep local

1. Confirm using df:

df -h | grep local

1. Add to /fstab for persistence:

server20:/common /local nfs _netdev 0 0

Note:

_netdev option makes system wait for networking to come up before trying to mount the share. 

1. Unmount share manually using umount then remount to validate accuracy of the entry in /fstab:

sudo umount /local
sudo mount -a

1. Verify:

df -h

1. Create a file in /local/ and verify:

touch /local/nfsfile
ls -l /local

1. Confirm the sync on server 2

ls -l /common/

5. Update fstab

Partitioning, MBR, and GPT

Partition Information (MBR and GPT)

• Partition information is stored on the disk in a small region.
• Read by the operating system at boot time.
• Master Boot Record (MBR) on the BIOS-based systems
• GUID Partition Table (GPT) on the UEFI-based systems.
• At system boot, the BIOS/UEFI:
  • scans all storage devices,
  • detects the presence of MBR/GPT areas,
  • identifies the boot disks,
  • loads the bootloader program in memory from the default boot disk,
  • executes the boot code to read the partition table and identify the /boot partition,
  • loads the kernel in memory, and passes control over to it.
• MBR and GPT store disk partition information and the boot code.

Master Boot Record (MBR)

• Resides on the first sector of the boot disk.

• was the preferred choice for saving partition table information on x86-based computers.

• with the arrival of bigger and larger hard drives, a new firmware specification (UEFI) was introduced.

• still widely used, but its use is diminishing in favor of UEFI.

• allows the creation of three types of partition on a single disk.

• primary, extended, and logical

• only primary and logical can be used for data storage

• extended is a mere enclosure for holding the logical partitions and it is not meant for data storage.

• supports the creation of up to four primary partitions numbered 1 through 4 at a time.

• In case additional partitions are required, one of the primary partitions must be deleted and replaced with an extended partition to be able to add logical partitions (up to 11) within that extended partition.

• Numbering for logical partitions begins at 5.

• supports a maximum of 14 usable partitions (3 primary and 11 logical) on a single disk.

• Cannot address storage space beyond 2TB due to its 32-bit nature and its 512-byte disk sector size.

• non-redundant; the record it contains is not replicated, resulting in an unbootable system in the event of corruption.

• If your disk is smaller than 2TB and you don’t intend to build more than 14 usable partitions, you can use MBR without issues.

GUID Partition Table (GPT)

• ability to construct up to 128 partitions (no concept of extended or logical partitions)
• utilize disks larger than 2TB
• use 4KB sector size
• store a copy of the partition information before the end of the disk for redundancy
• allows a BIOS-based system to boot from a GPT disk using the bootloader program stored in a protective MBR at the first disk sector
• UEFI firmware also supports the secure boot feature, which only allows signed binaries to boot

MBR Storage Management with parted

parted (partition editor)

• can be used to partition disks
• run interactively or directly from the command prompt.
• understands and supports both MBR and GPT schemes
• can be used to create up to 128 partitions on a single GPT disk
• viewing, labeling, adding, naming, and deleting partitions.

print
Displays the partition table that includes disk geometry and partition number, start and end, size, type, file system type, and relevant flags.

mklabel
Applies a label to the disk. Common labels are gpt and msdos.

mkpart
Makes a new partition

name
Assigns a name to a partition

rm
Removes the specified partition

• use the print subcommand to ensure you created what you wanted.
• /proc/partitions file is also updated to reflect the results of partition management operations.

Lab: Create an MBR Partition (server2)

• Assign partition type “msdos” to /dev/sdb for using it as an MBR disk
• create and confirm a 100MB primary partition on the disk.

1. Execute parted on /dev/sdb to view the current partition information:

[root@server2 ~]# sudo parted /dev/sdb print
Error: /dev/sdb: unrecognised disk label
Model: ATA VBOX HARDDISK (scsi)                                           
Disk /dev/sdb: 262MB
Sector size (logical/physical): 512B/512B
Partition Table: unknown
Disk Flags: 

There is an error on line 1 of the output, indicating an unrecognized label. disk must be labeled before it can be partitioned.

2. Assign disk label “msdos” to the disk with mklabel. This operation is performed only once on a disk.

[root@server2 ~]# sudo parted /dev/sdb mklabel msdos
Information: You may need to update /etc/fstab.

[root@server2 ~]# sudo parted /dev/sdb print                              
Model: ATA VBOX HARDDISK (scsi)
Disk /dev/sdb: 262MB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags: 

Number  Start  End  Size  Type  File system  Flags

To use the GPT partition table type, run “sudo parted /dev/sdb mklabel gpt” instead.

3. Create a 100MB primary partition starting at 1MB (beginning of the disk) using mkpart:

[root@server2 ~]# sudo parted /dev/sdb mkpart primary 1 101m
Information: You may need to update /etc/fstab.

4. Verify the new partition with print:

[root@server2 ~]# sudo parted /dev/sdb print                              
Model: ATA VBOX HARDDISK (scsi)
Disk /dev/sdb: 262MB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags: 

Number  Start   End    Size    Type     File system  Flags
 1      1049kB  101MB  99.6MB  primary

Partition numbering begins at 1 by default.

5. Confirm the new partition with the lsblk command:

[root@server2 ~]# lsblk /dev/sdb
NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
sdb      8:16   0  250M  0 disk 
└─sdb1   8:17   0   95M  0 part 

The device file for the first partition on the sdb disk is sdb1 as identified on the bottom line. The partition size is 95MB.

Different tools will have variance in reporting partition sizes. ignore minor differences.

6. Check the /proc/partitions file also:

[root@server2 ~]# cat /proc/partitions | grep sdb
   8       16     256000 sdb
   8       17      97280 sdb1

Exercise 13-3: Delete an MBR Partition (server2)

delete the sdb1 partition that was created in Exercise 13-2 confirm the deletion.

1. Execute parted on /dev/sdb with the rm subcommand to remove partition number 1:

[root@server2 ~]# sudo parted /dev/sdb rm 1
Information: You may need to update /etc/fstab.

2. Confirm the partition deletion with print:

[root@server2 ~]# sudo parted /dev/sdb print                              
Model: ATA VBOX HARDDISK (scsi)
Disk /dev/sdb: 262MB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags: 

Number  Start  End  Size  Type  File system  Flags

3. Check the /proc/partitions file:

[root@server2 ~]# cat /proc/partitions | grep sdb
   8       16     256000 sdb

can also run the lsblk command for further verification. T

EXAM TIP: Knowing either parted or gdisk for the exam is enough.

GPT Storage Management with gdisk

gdisk (GPT disk) Command

• partitions disks using the GPT format.

• text-based, menu-driven program

• show, add, verify, modify, and delete partitions

• can create up to 128 partitions on a single disk on systems with UEFI firmware.

• Main interface of gdisk can be invoked by specifying a disk device name such as /dev/sdc with the command. Type help or ? (question mark) at the prompt to view available subcommands.

[root@server2 ~]# sudo gdisk /dev/sdc
GPT fdisk (gdisk) version 1.0.7

Partition table scan:
  MBR: not present
  BSD: not present
  APM: not present
  GPT: not present

Creating new GPT entries in memory.

Command (? for help): ?
b	back up GPT data to a file
c	change a partition's name
d	delete a partition
i	show detailed information on a partition
l	list known partition types
n	add a new partition
o	create a new empty GUID partition table (GPT)
p	print the partition table
q	quit without saving changes
r	recovery and transformation options (experts only)
s	sort partitions
t	change a partition's type code
v	verify disk
w	write table to disk and exit
x	extra functionality (experts only)
?	print this menu

Command (? for help): 

Exercise 13-4: Create a GPT Partition (server2)

• Assign partition type “gpt” to /dev/sdc for using it as a GPT disk.
• create and confirm a 200MB partition on the disk.

1. Execute gdisk on /dev/sdc to view the current partition information:

[root@server2 ~]# sudo gdisk /dev/sdc
GPT fdisk (gdisk) version 1.0.7

Partition table scan:
  MBR: not present
  BSD: not present
  APM: not present
  GPT: not present

Creating new GPT entries in memory.

Command (? for help):

The disk currently does not have any partition table on it.

2. Assign “gpt” as the partition table type to the disk using the o subcommand. Enter “y” for confirmation to proceed. This operation is performed only once on a disk.

Command (? for help): o
This option deletes all partitions and creates a new protective MBR.
Proceed? (Y/N): y

3. Run the p subcommand to view disk information and confirm the GUID partition table creation:

Command (? for help): p
Disk /dev/sdc: 512000 sectors, 250.0 MiB
Model: VBOX HARDDISK   
Sector size (logical/physical): 512/512 bytes
Disk identifier (GUID): 9446222A-28AC-4F96-816F-518510F95019
Partition table holds up to 128 entries
Main partition table begins at sector 2 and ends at sector 33
First usable sector is 34, last usable sector is 511966
Partitions will be aligned on 2048-sector boundaries
Total free space is 511933 sectors (250.0 MiB)

Number  Start (sector)    End (sector)  Size       Code  Name

The output returns the assigned GUID and states that the partition table can hold up to 128 partition entries.

4. Create the first partition of size 200MB starting at the default sector with default type “Linux filesystem” using the n subcommand:

Command (? for help): n
Partition number (1-128, default 1): 
First sector (34-511966, default = 2048) or {+-}size{KMGTP}: 
Last sector (2048-511966, default = 511966) or {+-}size{KMGTP}: +200M
Current type is 8300 (Linux filesystem)
Hex code or GUID (L to show codes, Enter = 8300): 
Changed type of partition to 'Linux filesystem'

5. Verify the new partition with p:

Command (? for help): p
Disk /dev/sdc: 512000 sectors, 250.0 MiB
Model: VBOX HARDDISK   
Sector size (logical/physical): 512/512 bytes
Disk identifier (GUID): 9446222A-28AC-4F96-816F-518510F95019
Partition table holds up to 128 entries
Main partition table begins at sector 2 and ends at sector 33
First usable sector is 34, last usable sector is 511966
Partitions will be aligned on 2048-sector boundaries
Total free space is 102333 sectors (50.0 MiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1            2048          411647   200.0 MiB   8300  Linux filesystem

6. Run w to write the partition information to the partition table and exit out of the interface. Enter “y” to confirm when prompted.

Command (? for help): w

Final checks complete. About to write GPT data. THIS WILL OVERWRITE EXISTING
PARTITIONS!!

Do you want to proceed? (Y/N): y
OK; writing new GUID partition table (GPT) to /dev/sdc.
The operation has completed successfully.

You may need to run the partprobe command after exiting the gdisk utility to inform the kernel of partition table changes.

7. Verify the new partition by issuing either of the following at the command prompt:

[root@server2 ~]# grep sdc /proc/partitions
   8       32     256000 sdc
   8       33     204800 sdc1
   
[root@server2 ~]# lsblk /dev/sdc
NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
sdc      8:32   0  250M  0 disk 
└─sdc1   8:33   0  200M  0 part 

Exercise 13-5: Delete a GPT Partition(server2)

• Delete the sdc1 partition that was created in Exercise 13-4 and confirm the removal.

1. Execute gdisk on /dev/sdc and run d1 at the utility’s prompt to delete partition number 1:

[root@server2 ~]# gdisk /dev/sdc
GPT fdisk (gdisk) version 1.0.7

Partition table scan:
  MBR: protective
  BSD: not present
  APM: not present
  GPT: present

Found valid GPT with protective MBR; using GPT.

Command (? for help): d1
Using 1

2. Confirm the partition deletion with p:

Command (? for help): p
Disk /dev/sdc: 512000 sectors, 250.0 MiB
Model: VBOX HARDDISK   
Sector size (logical/physical): 512/512 bytes
Disk identifier (GUID): 9446222A-28AC-4F96-816F-518510F95019
Partition table holds up to 128 entries
Main partition table begins at sector 2 and ends at sector 33
First usable sector is 34, last usable sector is 511966
Partitions will be aligned on 2048-sector boundaries
Total free space is 511933 sectors (250.0 MiB)

Number  Start (sector)    End (sector)  Size       Code  Name

3. Write the updated partition information to the disk with w and quit gdisk:

Command (? for help): w

Final checks complete. About to write GPT data. THIS WILL OVERWRITE EXISTING
PARTITIONS!!

Do you want to proceed? (Y/N): y
OK; writing new GUID partition table (GPT) to /dev/sdc.
The operation has completed successfully.

4. Verify the partition deletion by issuing either of the following at the command prompt:

[root@server2 ~]# grep sdc /proc/partitions
   8       32     256000 sdc
[root@server2 ~]# lsblk /dev/sdc
NAME MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
sdc    8:32   0  250M  0 disk 

Disk Partitions

• Be careful when adding a new partition to elude data corruption with overlapping an extant partition or wasting storage by leaving unused space between adjacent partitions.
• Disk allocated at the time of installation is recognized as sda (s for SATA, SAS, or SCSI device) disk a, first partition identified as sda1 and the second partition as sda2.
• Any subsequent disks added to the system will be known as sdb, sdc, sdd, and so on, and will use 1, 2, 3, etc. for partition numbering.

Use lsblk to list disk and partition information.

[root@server1 ~]# lsblk
NAME          MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
sda             8:0    0   10G  0 disk 
├─sda1          8:1    0    1G  0 part /boot
└─sda2          8:2    0    9G  0 part 
  ├─rhel-root 253:0    0    8G  0 lvm  /
  └─rhel-swap 253:1    0    1G  0 lvm  [SWAP]
sr0            11:0    1  9.8G  0 rom  /mnt

sr0 represents the ISO image mounted as an optical medium:

[root@server1 ~]# sudo fdisk -l
Disk /dev/sda: 10 GiB, 10737418240 bytes, 20971520 sectors
Disk model: VBOX HARDDISK   
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0xfc8b3804

Device     Boot   Start      End  Sectors Size Id Type
/dev/sda1  *       2048  2099199  2097152   1G 83 Linux
/dev/sda2       2099200 20971519 18872320   9G 8e Linux LVM


Disk /dev/mapper/rhel-root: 8 GiB, 8585740288 bytes, 16769024 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/mapper/rhel-swap: 1 GiB, 1073741824 bytes, 2097152 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

identifiers 83 and 8e are hexadecimal values for the partition types

Storage Management Tools

parted, gdisk, and LVM Partitions created with a combination of most of these tools and toolsets can coexist on the same disk.

parted understands both MBR and GPT formats.

gdisk

• support the GPT format only
• may be used as a replacement of parted.

LVM

• feature-rich logical volume management solution that gives flexibility in storage management.

Remove a filesystem from a partition

Remove a filesystem from a partition

To delete a filesystem, partition, raid and disk labels from the disk. Use wipefs -a /dev/sdb1 May also use wipefs -a /dev/sdb? to delete sub partitions? (I need to verify this)

Make sure the filesystem is unmounted first.

[root@server2 mapper]# lsblk
NAME                    MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
sda                       8:0    0   20G  0 disk 
├─sda1                    8:1    0    1G  0 part 
└─sda2                    8:2    0   19G  0 part 
  ├─rhel-root           253:0    0   17G  0 lvm  /
  └─rhel-swap           253:1    0    2G  0 lvm  [SWAP]
sdb                       8:16   0  250M  0 disk 
├─sdb1                    8:17   0   95M  0 part 
├─sdb2                    8:18   0   95M  0 part 
└─sdb3                    8:19   0   38M  0 part [SWAP]
sdc                       8:32   0  250M  0 disk 
sdd                       8:48   0  250M  0 disk 
└─sdd1                    8:49   0  163M  0 part 
  ├─vgfs-ext4vol        253:2    0  128M  0 lvm  
  └─vgfs-xfsvol         253:3    0  128M  0 lvm  
sde                       8:64   0  250M  0 disk 
├─vgfs-ext4vol          253:2    0  128M  0 lvm  
├─vgfs-xfsvol           253:3    0  128M  0 lvm  
└─vgfs-swapvol          253:7    0  144M  0 lvm  [SWAP]
sdf                       8:80   0    5G  0 disk 
└─vgvdo1-vpool0_vdata   253:4    0    5G  0 lvm  
  └─vgvdo1-vpool0-vpool 253:5    0   20G  0 lvm  
    └─vgvdo1-lvvdo      253:6    0   20G  0 lvm  
sr0                      11:0    1  9.8G  0 rom  

[root@server2 mapper]# wipefs -a /dev/sdb1
/dev/sdb1: 2 bytes were erased at offset 0x00000438 (ext4): 53 ef

[root@server2 mapper]# wipefs -a /dev/sdb2
/dev/sdb2: 8 bytes were erased at offset 0x00000036 (vfat): 46 41 54 31 36 20 20 20
/dev/sdb2: 1 byte was erased at offset 0x00000000 (vfat): eb
/dev/sdb2: 2 bytes were erased at offset 0x000001fe (vfat): 55 aa

[root@server2 mapper]# wipefs -a /dev/sdb3
wipefs: error: /dev/sdb3: probing initialization failed: Device or resource busy

[root@server2 mapper]# wipefs -a /dev/sdb
wipefs: error: /dev/sdb: probing initialization failed: Device or resource busy

[root@server2 mapper]# swapoff /dev/sdb3

[root@server2 mapper]# wipefs -a /dev/sdb3
/dev/sdb3: 10 bytes were erased at offset 0x00000ff6 (swap): 53 57 41 50 53 50 41 43 45 32

[root@server2 mapper]# wipefs -a /dev/sdb
/dev/sdb: 2 bytes were erased at offset 0x000001fe (dos): 55 aa
/dev/sdb: calling ioctl to re-read partition table: Success

[root@server2 mapper]# lsblk
NAME                    MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
sda                       8:0    0   20G  0 disk 
├─sda1                    8:1    0    1G  0 part 
└─sda2                    8:2    0   19G  0 part 
  ├─rhel-root           253:0    0   17G  0 lvm  /
  └─rhel-swap           253:1    0    2G  0 lvm  [SWAP]
sdb                       8:16   0  250M  0 disk 
sdc                       8:32   0  250M  0 disk 
sdd                       8:48   0  250M  0 disk 
└─sdd1                    8:49   0  163M  0 part 
  ├─vgfs-ext4vol        253:2    0  128M  0 lvm  
  └─vgfs-xfsvol         253:3    0  128M  0 lvm  
sde                       8:64   0  250M  0 disk 
├─vgfs-ext4vol          253:2    0  128M  0 lvm  
├─vgfs-xfsvol           253:3    0  128M  0 lvm  
└─vgfs-swapvol          253:7    0  144M  0 lvm  [SWAP]
sdf                       8:80   0    5G  0 disk 
└─vgvdo1-vpool0_vdata   253:4    0    5G  0 lvm  
  └─vgvdo1-vpool0-vpool 253:5    0   20G  0 lvm  
    └─vgvdo1-lvvdo      253:6    0   20G  0 lvm  
sr0                      11:0    1  9.8G  0 rom  

I could not use this on a disk used in an LV. Remove the LVs: lvremove lvvdo vgfs

[root@server2 mapper]# lsblk
NAME           MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
sda              8:0    0   20G  0 disk 
├─sda1           8:1    0    1G  0 part 
└─sda2           8:2    0   19G  0 part 
  ├─rhel-root  253:0    0   17G  0 lvm  /
  └─rhel-swap  253:1    0    2G  0 lvm  [SWAP]
sdb              8:16   0  250M  0 disk 
sdc              8:32   0  250M  0 disk 
sdd              8:48   0  250M  0 disk 
└─sdd1           8:49   0  163M  0 part 
sde              8:64   0  250M  0 disk 
└─vgfs-swapvol 253:7    0  144M  0 lvm  [SWAP]
sdf              8:80   0    5G  0 disk 
sr0             11:0    1  9.8G  0 rom  

Need to remove swapvol from swap:

[root@server2 mapper]# swapoff /dev/mapper/vgfs-swapvol

Remove the LV:

[root@server2 mapper]# lvremove /dev/mapper/vgfs-swapvol
Do you really want to remove active logical volume vgfs/swapvol? [y/n]: y
  Logical volume "swapvol" successfully removed.

Wipe sdd:

[root@server2 mapper]# wipefs -a /dev/sdd
/dev/sdd: 2 bytes were erased at offset 0x000001fe (dos): 55 aa
/dev/sdd: calling ioctl to re-read partition table: Success
[root@server2 mapper]# lsblk
NAME          MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
sda             8:0    0   20G  0 disk 
├─sda1          8:1    0    1G  0 part 
└─sda2          8:2    0   19G  0 part 
  ├─rhel-root 253:0    0   17G  0 lvm  /
  └─rhel-swap 253:1    0    2G  0 lvm  [SWAP]
sdb             8:16   0  250M  0 disk 
sdc             8:32   0  250M  0 disk 
sdd             8:48   0  250M  0 disk 
sde             8:64   0  250M  0 disk 
sdf             8:80   0    5G  0 disk 
sr0            11:0    1  9.8G  0 rom  

Thin Provisioning and LVM

Thin Provisioning

• Allows for an economical allocation and utilization of storage space by moving arbitrary data blocks to contiguous locations, which results in empty block elimination.
• Can create a thin pool of storage space and assign volumes much larger storage space than the physical capacity of the pool.
• Workloads begin consuming the actual allocated space for data writing.
• When a preset custom threshold (80%, for instance) on the actual consumption of the physical storage in the pool is reached, expand the pool dynamically by adding more physical storage to it.
• The volumes will automatically start exploiting the new space right away.
• helps prevent spending more money upfront.

Logical Volume Manager (LVM)

• Used for managing block storage in Linux.
• Provides an abstraction layer between the physical storage and the file system
• Enables the file system to be resized, span across multiple disks, use arbitrary disk space, etc.
• Accumulates spaces taken from partitions or entire disks (called Physical Volumes) to form a logical container (called Volume Group) which is then divided into logical partitions (called Logical Volumes).
• online resizing of volume groups and logical volumes,
• online data migration between logical volumes and between physical volumes
• user-defined naming for volume groups and logical volumes
• mirroring and striping across multiple disks
• snapshotting of logical volumes.

• Made up of three key objects called physical volume, volume group, and logical volume.
• These objects are further virtually broken down into Physical Extents (PEs) and Logical Extents (LEs).

Physical Volume(PV)

• created when a block storage device such as a partition or an entire disk is initialized and brought under LVM control.
• This process constructs LVM data structures on the device, including a label on the second sector and metadata shortly thereafter.
• The label includes the UUID, size, and pointers to the locations of data and metadata areas.
• Given the criticality of metadata, LVM stores a copy of it at the end of the physical volume as well.
• The rest of the device space is available for use.

You can use an LVM command called pvs (physical volume scan or summary) to scan and list available physical volumes on server2:

[root@server2 ~]# sudo pvs
  PV         VG   Fmt  Attr PSize   PFree
  /dev/sda2  rhel lvm2 a--  <19.00g    0

• (a for allocatable under Attr)

Try running this command again with the -v flag to view more information about the physical volume.

Volume Group

• Created when at least one physical volume is added to it.
• The space from all physical volumes in a volume group is aggregated to form one large pool of storage, which is then used to build logical volumes.
• Physical volumes added to a volume group may be of varying sizes.
• LVM writes volume group metadata on each physical volume that is added to it.
• The volume group metadata contains its name,date, and time of creation, how it was created, the extent size used, a list of physical and logical volumes, a mapping of physical and logical extents, etc.
• Can have a custom name assigned to it at the time of its creation.
• A copy of the volume group metadata is stored and maintained at two distinct locations on each physical volume within the volume group.

Use vgs (volume group scan or summary) to scan and list available volume groups on server2:

[root@server2 ~]# sudo vgs
  VG   #PV #LV #SN Attr   VSize   VFree
  rhel   1   2   0 wz--n- <19.00g    0

• Status of the volume group under the Attr column (w for writeable, z for resizable, and n for normal),

Try running this command again with the -v flag to view more information about the volume group.

Physical Extent

• A physical volume is divided into several smaller logical pieces when it is added to a volume group.
• These logical pieces are known as Physical Extents (PE).
• An extent is the smallest allocatable unit of space in LVM.
• At the time of volume group creation, you can either define the size of the PE or leave it to the default value of 4MB.
• This implies that a 20GB physical volume would have approximately 5,000 PEs.
• Any physical volumes added to this volume group thereafter will use the same PE size.

Use vgdisplay (volume group display) on server2 and grep for ‘PE Size’ to view the PE size used in the rhel volume group:

[root@server2 ~]# sudo vgdisplay rhel | grep 'PE Size'
  PE Size               4.00 MiB

Logical Volume

• A volume group consists of a pool of storage taken from one or more physical volumes.
• This volume group space is used to create one or more Logical Volumes (LVs).
• A logical volume can be created or weeded out online, expanded or shrunk online, and can use space taken from one or multiple physical volumes inside the volume group.

The default naming convention used for logical volumes is lvol0, lvol1, lvol2, and so on you may assign custom names to them.

Use lvs (logical volume scan or summary) to scan and list available logical volumes on server2:

[root@server2 ~]# sudo lvs
  LV   VG   Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  root rhel -wi-ao---- <17.00g                                                    
  swap rhel -wi-ao----   2.00g

• Attr column (w for writeable, i for inherited allocation policy, a for active, and o for open) and their sizes.

Try running this command again with the -v flag to view more information about the logical volumes.

Logical Extent

• A logical volume is made up of Logical Extents (LE).
• Logical extents point to physical extents, and they may be random or contiguous.
• The larger a logical volume is, the more logical extents it will have.
• Logical extents are a set of physical extents allocated to a logical volume.
• The LE size is always the same as the PE size in a volume group.
• The default LE size is 4MB, which corresponds to the default PE size of 4MB.

Use lvdisplay (logical volume display) on server2 to view information about the root logical volume in the rhel volume group.

[root@server30 ~]# lvdisplay /dev/rhel/root
  --- Logical volume ---
  LV Path                /dev/rhel/root
  LV Name                root
  VG Name                rhel
  LV UUID                DhHyeI-VgwM-w75t-vRcC-5irj-AuHC-neryQf
  LV Write Access        read/write
  LV Creation host, time localhost.localdomain, 2024-07-08 17:32:18 -0700
  LV Status              available
  # open                 1
  LV Size                <17.00 GiB
  Current LE             4351
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:0

• The output does not disclose the LE size; however, you can convert the LV size in MBs (17,000) and then divide the result by the Current LE count (4,351) to get the LE size (which comes close to 4MB).

LVM Operations and Commands

• Creating and removing a physical volume, volume group, and logical volume
• Extending and reducing a volume group and logical volume
• Renaming a volume group and logical volume
• listing and displaying physical volume, volume group, and logical volume information.

Create and Remove Operations

pvcreate/pvremove

• Initializes/uninitializes a disk or partition for LVM use

vgcreate/vgremove

• Creates/removes a volume group

lvcreate/lvremove

• Creates/removes a logical volume

Extend and Reduce Operations

vgextend/vgreduce

• Adds/removes a physical volume to/from a volume group

lvextend/lvreduce

• Extends/reduces the size of a logical volume

lvresize

• Resizes a logical volume. With the -r option, this command calls the fsadm command to resize the underlying file system as well.

Rename Operations

vgrename

• Rename a volume group

lvrename

• Rename a logical volume

List and Display Operations

pvs/pvdisplay

• Lists/displays physical volume information

vgs/vgdisplay lvs/lvdisplay

• Lists/displays volume group information Lists/displays logical volume information

• All the tools accept the -v switch to support verbosity.

Exercise 13-6: Create Physical Volume and Volume Group (server2)

• initialize one partition sdd1 (90MB) and one disk sde (250MB) for use in LVM.
• create a volume group called vgbook and add both physical volumes to it use the PE size of 16MB
• list and display the volume group and the physical volumes.

1. Create a partition of size 90MB on sdd using the parted command and confirm. You need to label the disk first, as it is a new disk.

[root@server2 ~]# sudo parted /dev/sdd mklabel msdos
Information: You may need to update /etc/fstab.

[root@server2 ~]# sudo parted /dev/sdd mkpart primary 1 91m               
Information: You may need to update /etc/fstab.

[root@server2 ~]# sudo parted /dev/sdd print                              
Model: ATA VBOX HARDDISK (scsi)
Disk /dev/sdd: 262MB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags: 

Number  Start   End     Size    Type     File system  Flags
 1      1049kB  91.2MB  90.2MB  primary

2. Initialize the sdd1 partition and the sde disk using the pvcreate command. Note that there is no need to apply a disk label on sde with parted as LVM does not require it.

[root@server2 ~]# sudo pvcreate /dev/sdd1 /dev/sde -v
  Wiping signatures on new PV /dev/sdd1.
  Wiping signatures on new PV /dev/sde.
  Set up physical volume for "/dev/sdd1" with 176128 available sectors.
  Zeroing start of device /dev/sdd1.
  Writing physical volume data to disk "/dev/sdd1".
  Physical volume "/dev/sdd1" successfully created.
  Set up physical volume for "/dev/sde" with 512000 available sectors.
  Zeroing start of device /dev/sde.
  Writing physical volume data to disk "/dev/sde".
  Physical volume "/dev/sde" successfully created.

3. Create vgbook volume group using the vgcreate command and add the two physical volumes to it. Use the -s option to specify the PE size in MBs.

[root@server2 ~]# sudo vgcreate -vs 16 vgbook /dev/sdd1 /dev/sde
  Wiping signatures on new PV /dev/sdd1.
  Wiping signatures on new PV /dev/sde.
  Adding physical volume '/dev/sdd1' to volume group 'vgbook'
  Adding physical volume '/dev/sde' to volume group 'vgbook'
  Creating volume group backup "/etc/lvm/backup/vgbook" (seqno 1).
  Volume group "vgbook" successfully created

4. List the volume group information:

[root@server2 ~]# sudo vgs vgbook
  VG     #PV #LV #SN Attr   VSize   VFree  
  vgbook   2   0   0 wz--n- 320.00m 320.00m

5. Display detailed information about the volume group and the physical volumes it contains:

[root@server2 ~]# sudo vgdisplay -v vgbook
  --- Volume group ---
  VG Name               vgbook
  System ID             
  Format                lvm2
  Metadata Areas        2
  Metadata Sequence No  1
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                0
  Open LV               0
  Max PV                0
  Cur PV                2
  Act PV                2
  VG Size               320.00 MiB
  PE Size               16.00 MiB
  Total PE              20
  Alloc PE / Size       0 / 0   
  Free  PE / Size       20 / 320.00 MiB
  VG UUID               zRu1d2-ZgDL-bnzV-I9U1-0IFo-uM4x-w4bX0Q
   
  --- Physical volumes ---
  PV Name               /dev/sdd1     
  PV UUID               8x8IgZ-3z5T-ODA8-dofQ-xk5s-QN7I-KwpQ1e
  PV Status             allocatable
  Total PE / Free PE    5 / 5
   
  PV Name               /dev/sde     
  PV UUID               xJU0Hh-W5k9-FyKO-d6Ha-1ofW-ajvh-hJSo8R
  PV Status             allocatable
  Total PE / Free PE    15 / 15

6. List the physical volume information:

[root@server2 ~]# sudo pvs
  PV         VG     Fmt  Attr PSize   PFree  
  /dev/sda2  rhel   lvm2 a--  <19.00g      0 
  /dev/sdd1  vgbook lvm2 a--   80.00m  80.00m
  /dev/sde   vgbook lvm2 a--  240.00m 240.00m

7. Display detailed information about the physical volumes:

[root@server2 ~]# sudo pvdisplay /dev/sdd1
  --- Physical volume ---
  PV Name               /dev/sdd1
  VG Name               vgbook
  PV Size               86.00 MiB / not usable 6.00 MiB
  Allocatable           yes 
  PE Size               16.00 MiB
  Total PE              5
  Free PE               5
  Allocated PE          0
  PV UUID               8x8IgZ-3z5T-ODA8-dofQ-xk5s-QN7I-KwpQ1e

• Once a partition or disk is initialized and added to a volume group, they are treated identically within the volume group. LVM does not prefer one over the other.

Exercise 13-7: Create Logical Volumes(server2)

• Create two logical volumes, lvol0 and lvbook1, in the vgbook volume group.
• Use 120MB for lvol0 and 192MB for lvbook1 from the available pool of space.
• Display the details of the volume group and the logical volumes.

1. Create a logical volume with the default name lvol0 using the lvcreate command. Use the -L option to specify the logical volume size, 120MB. You may use the -v, -vv, or -vvv option with the command for verbosity.

root@server2 ~]# sudo lvcreate -vL 120 vgbook
  Rounding up size to full physical extent 128.00 MiB
  Creating logical volume lvol0
  Archiving volume group "vgbook" metadata (seqno 1).
  Activating logical volume vgbook/lvol0.
  activation/volume_list configuration setting not defined: Checking only host tags for vgbook/lvol0.
  Creating vgbook-lvol0
  Loading table for vgbook-lvol0 (253:2).
  Resuming vgbook-lvol0 (253:2).
  Wiping known signatures on logical volume vgbook/lvol0.
  Initializing 4.00 KiB of logical volume vgbook/lvol0 with value 0.
  Logical volume "lvol0" created.
  Creating volume group backup "/etc/lvm/backup/vgbook" (seqno 2).

• Size for the logical volume may be specified in units such as MBs, GBs, TBs, or as a count of LEs

• MB is the default if no unit is specified

• The size of a logical volume is always in multiples of the PE size. For instance, logical volumes created in vgbook with the PE size set at 16MB can be 16MB, 32MB, 48MB, 64MB, and so on.

2. Create lvbook1 of size 192MB (16x12) using the lvcreate command. Use the -l switch to specify the size in logical extents and -n for the custom name.

[root@server2 ~]# sudo lvcreate -l 12 -n lvbook1 vgbook
  Logical volume "lvbook1" created.

3. List the logical volume information:

[root@server2 ~]# sudo lvs
  LV      VG     Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  root    rhel   -wi-ao---- <17.00g                                                    
  swap    rhel   -wi-ao----   2.00g                                                    
  lvbook1 vgbook -wi-a----- 192.00m                                                    
  lvol0   vgbook -wi-a----- 128.00m 

4. Display detailed information about the volume group including the logical volumes and the physical volumes:

[root@server2 ~]# sudo vgdisplay -v vgbook
  --- Volume group ---
  VG Name               vgbook
  System ID             
  Format                lvm2
  Metadata Areas        2
  Metadata Sequence No  3
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                2
  Open LV               0
  Max PV                0
  Cur PV                2
  Act PV                2
  VG Size               320.00 MiB
  PE Size               16.00 MiB
  Total PE              20
  Alloc PE / Size       20 / 320.00 MiB
  Free  PE / Size       0 / 0   
  VG UUID               zRu1d2-ZgDL-bnzV-I9U1-0IFo-uM4x-w4bX0Q
   
  --- Logical volume ---
  LV Path                /dev/vgbook/lvol0
  LV Name                lvol0
  VG Name                vgbook
  LV UUID                9M9ahf-1L3y-c0yk-3Z2O-UzjH-0Amt-QLi4p5
  LV Write Access        read/write
  LV Creation host, time server2, 2024-06-12 02:42:51 -0700
  LV Status              available
  open                 0
  LV Size                128.00 MiB
  Current LE             8
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:2
   
  --- Logical volume ---
  LV Path                /dev/vgbook/lvbook1
  LV Name                lvbook1
  VG Name                vgbook
  LV UUID                pgd8qR-YXXK-3Idv-qmpW-w8Az-WGLR-g2d8Yn
  LV Write Access        read/write
  LV Creation host, time server2, 2024-06-12 02:45:31 -0700
  LV Status              available
  # open                 0
  LV Size                192.00 MiB
  Current LE             12
  Segments               2
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:3
   
  --- Physical volumes ---
  PV Name               /dev/sdd1     
  PV UUID               8x8IgZ-3z5T-ODA8-dofQ-xk5s-QN7I-KwpQ1e
  PV Status             allocatable
  Total PE / Free PE    5 / 0
   
  PV Name               /dev/sde     
  PV UUID               xJU0Hh-W5k9-FyKO-d6Ha-1ofW-ajvh-hJSo8R
  PV Status             allocatable
  Total PE / Free PE    15 / 0

Alternatively, you can run the following to view only the logical volume details:

[root@server2 ~]# sudo lvdisplay /dev/vgbook/lvol0
  --- Logical volume ---
  LV Path                /dev/vgbook/lvol0
  LV Name                lvol0
  VG Name                vgbook
  LV UUID                9M9ahf-1L3y-c0yk-3Z2O-UzjH-0Amt-QLi4p5
  LV Write Access        read/write
  LV Creation host, time server2, 2024-06-12 02:42:51 -0700
  LV Status              available
  # open                 0
  LV Size                128.00 MiB
  Current LE             8
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:2

[root@server2 ~]# sudo lvdisplay /dev/vgbook/lvbook1
  --- Logical volume ---
  LV Path                /dev/vgbook/lvbook1
  LV Name                lvbook1
  VG Name                vgbook
  LV UUID                pgd8qR-YXXK-3Idv-qmpW-w8Az-WGLR-g2d8Yn
  LV Write Access        read/write
  LV Creation host, time server2, 2024-06-12 02:45:31 -0700
  LV Status              available
  # open                 0
  LV Size                192.00 MiB
  Current LE             12
  Segments               2
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:3

Exercise 13-8: Extend a Volume Group and a Logical Volume(server2)

• Add another partition sdd2 of size 158MB to vgbook to increase the pool of allocatable space.
• Initialize the new partition prior to adding it to the volume group.
• Increase the size of lvbook1 to 336MB.
• Display basic information for the physical volumes, volume group, and logical volume.

1. Create a partition of size 158MB on sdd using the parted command. Display the new partition to confirm the partition number and size.

[root@server20 ~]# parted /dev/sdd mkpart primary 91 250

[root@server2 ~]# sudo parted /dev/sdd print                              
Model: ATA VBOX HARDDISK (scsi)
Disk /dev/sdd: 262MB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags: 

Number  Start   End     Size    Type     File system  Flags
 1      1049kB  91.2MB  90.2MB  primary
 2      92.3MB  250MB   157MB   primary               lvm

2. Initialize sdd2 using the pvcreate command:

[root@server2 ~]# sudo pvcreate /dev/sdd2
  Physical volume "/dev/sdd2" successfully created.

3. Extend vgbook by adding the new physical volume to it:

[root@server2 ~]# sudo vgextend vgbook /dev/sdd2
  Volume group "vgbook" successfully extended

4. List the volume group:

[root@server2 ~]# sudo vgs
  VG     #PV #LV #SN Attr   VSize   VFree  
  rhel     1   2   0 wz--n- <19.00g      0 
  vgbook   3   2   0 wz--n- 464.00m 144.00m

5. Extend the size of lvbook1 to 340MB by adding 144MB using the lvextend command:

[root@server2 ~]# sudo lvextend -L +144 /dev/vgbook/lvbook1
  Size of logical volume vgbook/lvbook1 changed from 192.00 MiB (12 extents) to 336.00 MiB (21 extents).
  Logical volume vgbook/lvbook1 successfully resized.

EXAM TIP: Make sure the expansion of a logical volume does not affect the file system and the data it contains.

6. Issue vgdisplay on vgbook with the -v switch for the updated details:

[root@server2 ~]# sudo vgdisplay -v vgbook
  --- Volume group ---
  VG Name               vgbook
  System ID             
  Format                lvm2
  Metadata Areas        3
  Metadata Sequence No  5
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                2
  Open LV               0
  Max PV                0
  Cur PV                3
  Act PV                3
  VG Size               464.00 MiB
  PE Size               16.00 MiB
  Total PE              29
  Alloc PE / Size       29 / 464.00 MiB
  Free  PE / Size       0 / 0   
  VG UUID               zRu1d2-ZgDL-bnzV-I9U1-0IFo-uM4x-w4bX0Q
   
  --- Logical volume ---
  LV Path                /dev/vgbook/lvol0
  LV Name                lvol0
  VG Name                vgbook
  LV UUID                9M9ahf-1L3y-c0yk-3Z2O-UzjH-0Amt-QLi4p5
  LV Write Access        read/write
  LV Creation host, time server2, 2024-06-12 02:42:51 -0700
  LV Status              available
  open                 0
  LV Size                128.00 MiB
  Current LE             8
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:2
   
  --- Logical volume ---
  LV Path                /dev/vgbook/lvbook1
  LV Name                lvbook1
  VG Name                vgbook
  LV UUID                pgd8qR-YXXK-3Idv-qmpW-w8Az-WGLR-g2d8Yn
  LV Write Access        read/write
  LV Creation host, time server2, 2024-06-12 02:45:31 -0700
  LV Status              available
  # open                 0
  LV Size                336.00 MiB
  Current LE             21
  Segments               3
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:3
   
  --- Physical volumes ---
  PV Name               /dev/sdd1     
  PV UUID               8x8IgZ-3z5T-ODA8-dofQ-xk5s-QN7I-KwpQ1e
  PV Status             allocatable
  Total PE / Free PE    5 / 0
   
  PV Name               /dev/sde     
  PV UUID               xJU0Hh-W5k9-FyKO-d6Ha-1ofW-ajvh-hJSo8R
  PV Status             allocatable
  Total PE / Free PE    15 / 0
   
  PV Name               /dev/sdd2     
  PV UUID               1olOnk-o8FH-uJRD-2pJf-8GCy-3K0M-gcf3pF
  PV Status             allocatable
  Total PE / Free PE    9 / 0

7. View a summary of the physical volumes:

root@server2 ~]# sudo pvs
  PV         VG     Fmt  Attr PSize   PFree
  /dev/sda2  rhel   lvm2 a--  <19.00g    0 
  /dev/sdd1  vgbook lvm2 a--   80.00m    0 
  /dev/sdd2  vgbook lvm2 a--  144.00m    0 
  /dev/sde   vgbook lvm2 a--  240.00m    0

8. View a summary of the logical volumes:

[root@server2 ~]# sudo lvs
  LV      VG     Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  root    rhel   -wi-ao---- <17.00g                                                    
  swap    rhel   -wi-ao----   2.00g                                                    
  lvbook1 vgbook -wi-a----- 336.00m                                                    
  lvol0   vgbook -wi-a----- 128.00m 

Exercise 13-9: Rename, Reduce, Extend, and Remove Logical Volumes(server2)

• Rename lvol0 to lvbook2.
• Decrease the size of lvbook2 to 50MB using the lvreduce command
• Add 32MB with the lvresize command.
• remove both logical volumes.
• display the summary for the volume groups, logical volumes, and physical volumes.

1. Rename lvol0 to lvbook2 using the lvrename command and confirm with lvs:

[root@server2 ~]# sudo lvrename vgbook lvol0 lvbook2
  Renamed "lvol0" to "lvbook2" in volume group "vgbook"

2. Reduce the size of lvbook2 to 50MB with the lvreduce command. Specify the absolute desired size for the logical volume. Answer “Do you really want to reduce vgbook/lvbook2?” in the affirmative.

[root@server2 ~]# sudo lvreduce -L 50 /dev/vgbook/lvbook2
  Rounding size to boundary between physical extents: 64.00 MiB.
  No file system found on /dev/vgbook/lvbook2.
  Size of logical volume vgbook/lvbook2 changed from 128.00 MiB (8 extents) to 64.00 MiB (4 extents).
  Logical volume vgbook/lvbook2 successfully resized.

3. Add 32MB to lvbook2 with the lvresize command:

[root@server2 ~]# sudo lvresize -L +32 /dev/vgbook/lvbook2
  Size of logical volume vgbook/lvbook2 changed from 64.00 MiB (4 extents) to 96.00 MiB (6 extents).
  Logical volume vgbook/lvbook2 successfully resized.

4. Use the pvs, lvs, vgs, and vgdisplay commands to view the updated allocation.

[root@server2 ~]# pvs
  PV         VG     Fmt  Attr PSize   PFree 
  /dev/sda2  rhel   lvm2 a--  <19.00g     0 
  /dev/sdd1  vgbook lvm2 a--   80.00m     0 
  /dev/sdd2  vgbook lvm2 a--  144.00m     0 
  /dev/sde   vgbook lvm2 a--  240.00m 32.00m
  
[root@server2 ~]# lvs
  LV      VG     Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  root    rhel   -wi-ao---- <17.00g                                                    
  swap    rhel   -wi-ao----   2.00g                                                    
  lvbook1 vgbook -wi-a----- 336.00m                                                    
  lvbook2 vgbook -wi-a-----  96.00m  
 
[root@server2 ~]# vgs
  VG     #PV #LV #SN Attr   VSize   VFree 
  rhel     1   2   0 wz--n- <19.00g     0 
  vgbook   3   2   0 wz--n- 464.00m 32.00m
  
[root@server2 ~]# vgdisplay
  --- Volume group ---
  VG Name               vgbook
  System ID             
  Format                lvm2
  Metadata Areas        3
  Metadata Sequence No  8
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                2
  Open LV               0
  Max PV                0
  Cur PV                3
  Act PV                3
  VG Size               464.00 MiB
  PE Size               16.00 MiB
  Total PE              29
  Alloc PE / Size       27 / 432.00 MiB
  Free  PE / Size       2 / 32.00 MiB
  VG UUID               zRu1d2-ZgDL-bnzV-I9U1-0IFo-uM4x-w4bX0Q
   
  --- Volume group ---
  VG Name               rhel
  System ID             
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  3
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                2
  Open LV               2
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               <19.00 GiB
  PE Size               4.00 MiB
  Total PE              4863
  Alloc PE / Size       4863 / <19.00 GiB
  Free  PE / Size       0 / 0   
  VG UUID               UiK3fy-FGOc-2fnP-C1Y6-JS0l-irEe-Sq3c4h

5. Remove both lvbook1 and lvbook2 logical volumes using the lvremove command. Use the -f option to suppress the “Do you really want to remove active logical volume” message.

[root@server2 ~]# sudo lvremove /dev/vgbook/lvbook1 -f
  Logical volume "lvbook1" successfully removed.
[root@server2 ~]# sudo lvremove /dev/vgbook/lvbook2 -f
  Logical volume "lvbook2" successfully removed.

• Removing an LV is destructive
• Backup any data in the target LV before deleting it.
• You will need to unmount the file system or disable swap in the logical volume.
  6. Execute the vgdisplay command and grep for “Cur LV” to see the number of logical volumes currently available in vgbook. It should show 0, as you have removed both logical volumes.

[root@server2 ~]# sudo vgdisplay vgbook | grep 'Cur LV'
  Cur LV                0

Exercise 13-10: Reduce and Remove a Volume Group(server2)

\

• Reduce vgbook by removing the sdd1 and sde physical volumes from it
• Remove the volume group.
• Confirm the deletion of the volume group and the logical volumes at the end.

1. Remove sdd1 and sde physical volumes from vgbook by issuing the vgreduce command:

[root@server2 ~]# sudo vgreduce vgbook /dev/sdd1 /dev/sde
  Removed "/dev/sdd1" from volume group "vgbook"
  Removed "/dev/sde" from volume group "vgbook"

2. Remove the volume group using the vgremove command. This will also remove the last physical volume, sdd2, from it.

[root@server2 ~]# sudo vgremove vgbook
  Volume group "vgbook" successfully removed

• Use the -f option with the vgremove command to force the volume group removal even if it contains any number of logical and physical volumes in it.

3. Execute the vgs and lvs commands for confirmation:

[root@server2 ~]# sudo vgs
  VG   #PV #LV #SN Attr   VSize   VFree
  rhel   1   2   0 wz--n- <19.00g    0 
[root@server2 ~]# sudo lvs
  LV   VG   Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  root rhel -wi-ao---- <17.00g                                                    
  swap rhel -wi-ao----   2.00g    

Exercise 13-11: Uninitialize Physical Volumes (Server2)\

• Uninitialize all three physical volumes—sdd1, sdd2, and sde—by deleting the LVM structural information from them.
• Use the pvs command for confirmation.
• Remove the partitions from the sdd disk and
• Verify that all disks used in Exercises 13-6 to 13-10 are now in their original raw state.

1. Remove the LVM structures from sdd1, sdd2, and sde using the pvremove command:

[root@server2 ~]# sudo pvremove /dev/sdd1 /dev/sdd2 /dev/sde
  Labels on physical volume "/dev/sdd1" successfully wiped.
  Labels on physical volume "/dev/sdd2" successfully wiped.
  Labels on physical volume "/dev/sde" successfully wiped.

2. Confirm the removal using the pvs command:

[root@server2 ~]# sudo pvs
  PV         VG   Fmt  Attr PSize   PFree
  /dev/sda2  rhel lvm2 a--  <19.00g    0 

The partitions and the disk are now back to their raw state and can be repurposed.

3. Remove the partitions from sdd using the parted command:

[root@server2 ~]# sudo parted /dev/sdd rm 1 ; sudo parted /dev/sdd rm 2
Information: You may need to update /etc/fstab.

Information: You may need to update /etc/fstab.  

4. Verify that all disks used in previous exercises have returned to their original raw state using the lsblk command:

[root@server2 ~]# lsblk                                                   
NAME          MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
sda             8:0    0   20G  0 disk 
├─sda1          8:1    0    1G  0 part /boot
└─sda2          8:2    0   19G  0 part 
  ├─rhel-root 253:0    0   17G  0 lvm  /
  └─rhel-swap 253:1    0    2G  0 lvm  [SWAP]
sdb             8:16   0  250M  0 disk 
sdc             8:32   0  250M  0 disk 
sdd             8:48   0  250M  0 disk 
sde             8:64   0  250M  0 disk 
sdf             8:80   0    5G  0 disk 
sr0            11:0    1  9.8G  0 rom  

Virtual Data Optimizer (VDO)

• Used for storage optimization
• Device driver layer that sits between the Linux kernel and the physical storage devices.
• Conserve disk space, improve data throughput, and save on storage cost.
• Employs thin provisioning, de-duplication, and compression technologies to help realize the goals.

How VDO Conserves Storage

Stage 1

• Makes use of thin provisioning to identify and eliminate empty (zero-byte) data blocks. (zero-block elimination)
• Removes randomization of data blocks by moving in-use data blocks to contiguous locations on the storage device.

Stage 2

• If it detects that new data is an identical copy of some existing data, it makes an internal note of it but does not actually write the redundant data to the disk. (de-duplication)
• Implemented with the inclusion of a kernel module called UDS (Universal De-duplication Service).

Stage 3

• Calls upon another kernel module called kvdo, which compresses the residual data blocks and consolidates them on a lower number of blocks.
• Results in a further drop in storage space utilization.
• Runs in the background and processes inbound data through the three stages on VDO-enabled volumes.
• Not a CPU or memory-intensive process

VDO Integration with LVM

• LVM utilities have been enhanced to include options to support VDO volumes.

VDO Components

• Utilizes the concepts of pool and volume. pool
• logical volume that is created inside an LVM volume group using a deduplicated storage space. volume
• Just like a regular LVM logical volume, but it is provisioned in a pool.
• Needs to be formatted with file system structures before it can be used.

vdo and kmod-kvdo Commands

• Create, mount, and manage LVM VDO volumes
• Installed on the system by default.

vdo

• Installs the tools necessary to support the creation and management of VDO volumes

kmod-kvdo

• Implements fine-grained storage virtualization, thin provisioning, and compression. Not installed by default?