Master NFS: Configure, Manage, and Optimize Network File Systems on Linux

NFS Overview

Network File System (NFS) 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 Remote Procedure Call (RPC) in a client‑server model.

NFS advantages include saving local storage space by placing frequently used directories such as /home on an NFS server, which can be accessed over the network.

NFS Software Packages

Package: nfs-utils (includes server and client tools; not installed by default on minimal CentOS 8)
Related packages: rpcbind (required), tcp_wrappers
Kernel module: nfs.ko
Ports: 2049 (nfsd), other ports assigned by portmap (111)
Key NFS daemons:
  rpc.nfsd   – main NFS daemon, controls client access
  rpc.mountd – handles mount/unmount 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 Export File Format

/dir  host1(opt1,opt2)  host2(opt1,opt2) …

Lines beginning with # are comments. Host specifications can be: * – wildcard for all clients

IPv4, IPv6, or FQDN

IP networks in CIDR or netmask form (e.g., 172.31.0.0/255.255.0.0 or 172.31.0.0/16)

Wildcards in hostnames (e.g., *.example.com) – not allowed for IPs

Netgroups: @group_name Typical export options:

Default: (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 since NFS 1.0, safer)
root_squash           – maps remote root to uid 65534 (nfsnobody)
no_root_squash        – remote root retains root privileges
all_squash            – maps all remote users to anonymous uid/gid
no_all_squash         – preserves original uid/gid
anonuid, anongid      – map anonymous user to specific uid/gid

Example Export Entries

/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.

rpcinfo -p hostname   # list registered RPC services
rpcinfo -s hostname   # show registered programs

exportfs

Manages NFS exports.

-v   # show all NFS shares on the local host
-r   # re‑read the export file and share directories
-a   # list all current exports
-au  # unexport all shares

showmount

Shows NFS shares on a remote host.

# showmount -e hostname

mount.nfs (Client Mount)

Common mount options (see man 5 nfs):

fg          # foreground mount (default)
bg          # background mount
hard        # keep trying on failure (default)
soft        # fail after timeout
intr        # allow interrupting hard mounts
rsize/wsize # max bytes per read/write (default 32768)
_netdev     # do not mount until network is up
vers=4.2    # specify NFS version (CentOS 8 defaults to 4.2)

Security‑oriented recommendation: use nosuid,netdev,noexec options.

Mount Examples

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

# Persistent mount via /etc/fstab
172.16.0.1:/public /mnt/nfs nfs defaults,_netdev 0 0

Practical Case: Setting Up NFS with autofs

# On NFS server
mkdir -pv /data/home
useradd -d /data/home/user1 -u 2000 user1
echo "/data/home *(rw)" > /etc/exports.d/test.exports
exportfs -r

# On first client (relative‑path autofs)
useradd -M -u 2000 user1
echo "/home /etc/auto.home" >> /etc/auto.master
echo "* -fstype=nfs,vers=3 172.31.0.8:/data/home/&" > /etc/auto.home
systemctl restart autofs

# Verify mount
su - user1
df -T /home/user1

# On second client (absolute‑path autofs)
useradd -M -u 2000 user1
echo "/- /etc/auto.home" >> /etc/auto.master
echo "/home/user1 -fstype=nfs,vers=3 nfsserver:/data/home/user1" > /etc/auto.home
service autofs restart
su - user1
df -T /home/user1