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/
  1. Update fstab