Mastering NFS: How to Configure Network File System on Linux

NFS (Network File System) is a kernel‑based file system developed by Sun Microsystems that allows users and programs to access remote files as if they were local, using RPC (Remote Procedure Call) in a client‑server model.

Advantages of NFS include saving local storage space by placing commonly used data such as the /home directory on an NFS server, which can be accessed over the network.

NFS Software Overview

Software package: nfs-utils (includes server and client tools; not installed by default on minimal CentOS 8)
Related packages: rpcbind (required), tcp_wrappers
Kernel support: nfs.ko
Ports: 2049 (nfsd), other ports allocated by portmap (111)
Main NFS processes:
  rpc.nfsd      – primary NFS daemon, manages client access
  rpc.mountd    – handles mounting/unmounting and permission management
  rpc.lockd    – optional, manages file locking
  rpc.statd    – optional, checks and repairs file consistency
Log directory: /var/lib/nfs/
Configuration files:
  /etc/exports
  /etc/exports.d/*.exports

NFS sharing configuration file format: /dir host1(opt1,opt2) host2(opt1,opt2)... Format notes:

Lines starting with # are comments.

Host specifications can be:

anonymous – represented by * to match all clients

Single host – IPv4, IPv6, or FQDN

IP networks – both CIDR and netmask styles are supported (e.g., 172.31.0.0/255.255.0.0 or 172.31.0.0/16)

Wildcards – hostname patterns such as *.example.com (IP wildcards are not allowed)

Netgroups – NIS domain groups, prefixed with @

Default export options: (ro,sync,root_squash,no_all_squash)

ro / rw – read‑only or read‑write

async – asynchronous writes (higher performance, lower safety)

sync – synchronous writes (default after NFS 1.0, safer but slower)

root_squash – maps remote root to nfsnobody (UID 65534)

no_root_squash – preserves remote root UID

all_squash – maps all remote users to anonymous UID/GID

no_all_squash – keeps original UID/GID

anonuid / anongid – specify custom anonymous UID/GID

Example NFS export configuration:

/myshare server.example.com
/myshare *.example.com
/myshare server?.example.com
/myshare server[0-20].example.com
/myshare 172.25.11.10
/myshare 172.25.0.0/16
/myshare 2000:472:18:b51:c32:a21
/myshare 2000:472:18:b51::/64
/myshare *.example.com 172.25.0.0/16
/myshare desktop.example.com(ro)
/myshare desktop.example.com(ro) server[0-20].example.com(rw)
/myshare diskless.example.com(rw,no_root_squash)

NFS Tools

rpcinfo – displays RPC program information on a host. rpcinfo -p hostname Shows registered RPC services and their ports.

exportfs

Manages NFS exported file systems.

-v   # view all NFS shares on the local machine
-r   # re‑read configuration files and export directories
-a   # list all current exports
-au  # stop all local exports

showmount

Displays NFS shares on a remote host.

# showmount -e hostname

mount.nfs (client mounting)

Common mount options (see man 5 nfs):

fg – foreground mount (default)

bg – background mount

hard – persistent requests (default)

soft – non‑persistent requests

intr – allows interruption of hard mounts

rsize / wsize – maximum bytes per read/write (default rsize=32768)

_netdev – do not mount until network is available

vers – specify NFS version (CentOS 8 defaults to 4.2, CentOS 7 to 4.1, CentOS 6 to 4.0)

Example temporary mount:

# mount -o rw,nosuid,fg,hard,intr 172.31.0.8:/testdir /mnt/nfs/

Example entry for automatic mounting at boot (in /etc/fstab):

172.16.0.1:/public  /mnt/nfs  nfs  defaults,_netdev  0 0

Case Study: Step‑by‑Step Setup

# On the NFS server, create a user and home directory to share
mkdir -pv /data/home
useradd -d /data/home/user1 -u 2000 user1
# Define export (e.g., /etc/exports.d/test.exports)
/data/home *(rw)
exportfs -r
# On client 1 (172.31.0.7) configure autofs for relative paths
vim /etc/auto.master
/home /etc/auto.home
vim /etc/auto.home
* -fstype=nfs,vers=3 172.31.0.8:/data/home/&
systemctl restart autofs
# Verify mount
df -T /home/user1
# On client 2 (172.31.0.6) configure autofs for absolute paths
vim /etc/auto.master
/- /etc/auto.home
vim /etc/auto.home
/home/user1 -fstype=nfs,vers=3 nfsserver:/data/home/user1
service autofs restart
# Verify mount
df -T /home/user1

These steps demonstrate creating NFS exports, reloading the configuration, and using autofs on multiple clients to automatically mount user home directories.