RunBook AcademyLinux

Linux XVIII · Enterprise StorageNFS

NFS client - mounting and operating network filesystems

Intermediate⏱ ~10 minbashmountshowmountnfsstat

What you'll learn

Mount an NFS export with appropriate options
Use _netdev and nofail for safe boot behavior
Troubleshoot common NFS mount failures
Configure NFS for production workloads

Prerequisites

Verified against Ubuntu 24.04 LTS · Debian 12 (Bookworm) · RHEL 9.x · Rocky Linux 9.x · AlmaLinux 9.x · Linux kernel 6.1 LTS / 6.6 LTS · systemd 255+ · OpenSSH 8.7p1 (RHEL 9) / 9.6p1 (Ubuntu 24.04) · nftables 1.0.x · chrony 4.x · Pacemaker 2.1.x · Corosync 3.1.x · 2026-08-09

Not yet marked complete on this device.

NFS is the standard Linux network filesystem. The NFS client mounts a remote export and presents it as a local directory. Understanding the mount options, the network dependencies, and the failure modes is essential for production.

Discovering exports

Read-only / Safeshowmount -e— showmount -e lists the exports available on an NFS server. The IP-range column shows which clients are allowed to mount each export. Confirm the export exists and your client is in the allowed range before trying to mount.

$ showmount -e nfs-server.example.com

Export list for nfs-server.example.com:
/export/data  10.0.0.0/24
/export/home  10.0.0.0/24

Mounting an NFS export

Configuration changemount NFS— vers=4.1 is the modern NFS. proto=tcp forces TCP transport. rsize/wsize 1MB matches the server's block size for maximum throughput. hard means the client retries indefinitely on failure (vs soft which returns an error). timeo=600 sets the timeout to 60 seconds (10 deciseconds).

$ mount -t nfs -o vers=4.1,proto=tcp,rsize=1048576,wsize=1048576,hard,timeo=600 nfs-server:/export/data /mnt/nfs

fstab entry

Read-only / SafeNFS in fstab— fstab entry for NFS. vers=4.1 (or nfs4 in fstab). _netdev waits for the network. nofail continues boot if the mount fails. hard retries indefinitely. timeo=600 and retrans=3 set retry parameters. pass 0 skips fsck at boot (NFS does not need fsck).

$ grep nfs /etc/fstab

nfs-server:/export/data /mnt/nfs nfs4 _netdev,nofail,hard,timeo=600,retrans=3 0 0

NFS mount options

Option	Effect	When to use
`vers=4.1` (or `vers=4.2`)	NFS version	Required for modern kernels
`proto=tcp`	TCP transport	Required for NFSv4
`rsize=N` / `wsize=N`	Read/write block size	Match to server (1 MB typical)
`hard`	Retry indefinitely on failure	Production: avoid silent data loss
`soft`	Return error after timeout	Avoid in production
`timeo=N`	Timeout in deciseconds (60 = 6 sec)	Default 60, increase to 600 for slow links
`retrans=N`	Number of retries	Default 3, increase to 6 for unreliable links
`rsize=1048576,wsize=1048576`	1 MB block size	Match to server MTU
`lookupcache=pos` or `lookupcache=none`	Caching mode	`pos` for POSIX; `none` for changing data
`noacl`	Disable ACL processing	When ACLs are not needed
`sec=sys` / `sec=krb5`	Security mode	`sys` for local; `krb5` for Kerberos

Troubleshooting NFS mount failures

Read-only / Safemount verbose— mount -v shows the verbose output. The connection refused error means the NFS server is not responding on the expected port. Check the server's NFS service, firewall rules, and network connectivity.

$ mount -v -t nfs nfs-server:/export/data /mnt/nfs 2>&1 | head -10

mount.nfs: timeout set for Sat Jan 15 10:00:00 2026
mount.nfs: trying text-based options 'vers=4.1,addr=10.0.0.10,clientaddr=10.0.0.20'
mount.nfs: mount(2): Connection refused

Symptom	Likely cause	Fix
Connection refused	NFS service not running, firewall	`systemctl status nfs-server` and check firewall
Connection timed out	Network issue, no route	`ping nfs-server`, check routing
Permission denied	Export does not allow your client IP	Check `/etc/exports` on server, add your client IP
Stale file handle	NFS server lost the export, client has open files	`umount /mnt/nfs` and remount
No such file or directory	Export path is wrong on server	Check `/etc/exports` on server

Knowledge check