Managing Partitions and LVM

After detecting the disk device that needs to be used, you can move on and start creating partitions and logical volumes.

partition a disk using the parted module,
work with the lvg and lvol modules to manage LVM logical volumes,
create file systems using the filesystem module and mount them using the mount module
manage swap storage.

Creating Partitions

Parted Module name:

Assign unique name, required for GPT partitions label:
type of partition table, msdos is default, gpt for gpt device:
Device where you are creating partition number:
partition number state:
present or absent to add/remove

part_start:

Starting position expressed as an offset from the beginning of the disk part_end:
Where to end the partition If these arguments are not used, the partition starts at 0% and ends at 100% of the available disk space.

flags:

Set specific partition properties such as LVM partition type.
Required for LVM partition type

      - name: create new partition
        parted:
          name: files
          label: gpt
          device: /dev/sdb
          number: 1
          state: present
          part_start: 1MiB
          part_end: 2GiB
      - name: create another new partition
        parted:
          name: swap
          label: gpt
          device: /dev/sdb
          number: 2
          state: present
          part_start: 2GiB
          part_end: 4GiB
          flags: [ lvm ]

Managing Volume Groups and LVM Logical Volumes

lvg module

manage LVM logical volumes
managing LVM volume groups

lvol module

managing LVM logical volumes.

Creating an LVM volume group

vg argument to set the name of the volume group
pvs argument to identify the physical volume (which is often a partition or a disk device) on which the volume group needs to be created.
May need to specify the pesize to refer to the size of the physical extents.

- name: create a volume group
  lvg:
    vg: vgdata
    pesize: "8"
    pvs: /dev/sdb1

After you create an LVM volume group, you can create LVM logical volumes.

lvol Common Options: lv

Name of the LV pvs
comma separated list of pvs, if it is a partition then it should have the lvm option set resizefs
Indicates whether to resize filesystem when the lv is expanded size
size of the lv snapshot
specify name if this lv is a snapshot vg
VG is which the lv should be created

Creating an LVM Logical Volume

- name: create a logical volume
    lvol:
      lv: lvdata
      size: 100%FREE
      vg: vgdata

Creating and Mounting File Systems

filesystem module

Supports creating as well as resizing file systems.

Options: dev

block device name fstype
filesystem type opts
options passed to mkfs command resizefs
Extends the filesystem if set to yes. Extended to the current block size

Creating an XFS File System

- name: create an XFS filesystem
  filesystem:
    dev: /dev/vgdata/lvdata
    fstype: xfs

Mounting a filesystem

mount module.

Used to mount a filesystem

Options: fstype

Filesystem type is not automatically dedected.
Used to specify filesystem type path
directory to mount the filesystem to src
device to be mounted state
Current mount state
mounted to mount device now
present to set in /etc/fstab but not mount it now

      - name: mount the filesystem
        mount:
          src: /dev/vgdata/lvdata
          fstype: xfs
          state: mounted
          path: /mydir

Configuring Swap Space

To set up swap space, you first must format a device as swap space and next mount the swap space.
To format a device as swap space, you use the filesystem module.
There is no specific Ansible module to activate theswap space, so you use the command module to run the Linux swapon command.
Because adding swap space is not always required, it can be done in a conditional statement.
In the statement, use the ansible_swaptotal_mb fact to discover how much swap is actually available.
If that amount falls below a specific threshold, the swap space can be created and activated.

A conditional check is performed, and additional swap space is configured if the current amount of swap space is lower than 256 MiB.

    ---
    - name: configure swap storage
      hosts: ansible2
      tasks:
      - name: setup swap
        block:
        - name: make the swap filesystem
          filesystem:
            fstype: swap
            dev: /dev/sdb1
        - name: activate swap space
          command: swapon /dev/sdb1
        when: ansible_swaptotal_mb < 256

Run an ad hoc command to ensure that /dev/sdb on the target host is empty:

ansible ansible2 -a "dd if=/dev/zero of=/dev/sdb bs=1M count=10"

To make sure that you don’t get any errors about partitions that are in use, also reboot the target host:

ansible ansible2 -m reboot

Lack of idempotency if the size is specified as 100%FREE, which is a relative value, not an absolute value.
This value works the first time you run the playbook, but it does not the second time you run the playbook.
Because no free space is available, the LVM layer interprets the task as if you wanted to create a logical volume with a size of 0 MiB and will complain about that. To ensure that plays are written in an idempotent way, make sure that you use absolute values, not relative values.