CentOS / RHEL 7 : Configuring an NFS server and NFS client Linux NFS

NFS allows a linux server to share directories with other UNIX clients over network. NFS server exports a directory and NFS client mounts this directory. RHEL 7 supports two version of NFS – NFSv3 and NFSv4.

NFS server and RPC processes

starting the nfs-server process starts the NFS server and other RPC processes. RPC processes includes:
rpc.statd : implements monitoring protocol (NSM) between NFS client and NFS server
rpc.mountd : NFS mount daemon that implements the server side of the mount requests from NFSv3 clients.
rpc.idmapd : Maps NFSv4 names and local UIDs and GIDs
rpc.rquotad : provides user quota information for remote users.

Configuring NFS server

1. Install the required nfs packages if not already installed on the server :

# rpm -qa | grep nfs-utils
# yum install nfs-utils rpcbind

2. Enable the services at boot time:

#  systemctl enable nfs-server
#  systemctl enable rpcbind
#  systemctl enable nfs-lock

In RHEL7.1 (nfs-utils-1.3.0-8.el7) enabling nfs-lock does not work (No such file or directory). it does not need to be enabled since rpc-statd.service is static.

#  systemctl enable nfs-idmap

In RHEL7.1 (nfs-utils-1.3.0-8.el7) this does not work (No such file or directory). it does not need to be enabled since nfs-idmapd.service is static.

3. Start the NFS services:

#  systemctl start rpcbind
#  systemctl start nfs-server
#  systemctl start nfs-lock
#  systemctl start nfs-idmap

4. Check the status of NFS service:

# systemctl status nfs

5. Create a shared directory:

# mkdir /test

6. Export the directory. The format of the /etc/exports file is :

dir client1 (options) [client2(options)...]

Client options include (defaults are listed first) :
ro / rw :
a) ro : allow clients read only access to the share.
b) rw : allow clients read write access to the share.
sync / async :
a) sync : NFS server replies to request only after changes made by previous request are written to disk.
b) async : specifies that the server does not have to wait.
wdelay / no_wdelay
a) wdelay : NFS server delays committing write requests when it suspects another write request is imminent.
b) no_wdelay : use this option to disable to the delay. no_wdelay option can only be enabled if default sync option is enabled.
no_all_squash / all_squash :
a) no_all_squash : does not change the mapping of remote users.
b) all_squash : to squash all remote users including root.
root_squash / no_root_squash :
a) root_squash : prevent root users connected remotely from having root access. Effectively squashing remote root privileges.
b) no_root_squash : disable root squashing.

Example :

# vi /etc/exports
/test *(rw)

7. Exporting the share :

# exportfs -r

-r re-exports entries in /etc/exports and sync /var/lib/nfs/etab with /etc/exports. The /var/lib/nfs/etab is the master export table. Other options that can be used with exportfs command are :

-a : exports entries in /etc/exports but do not synchronize with /var/lib/nfs/etab
-i : ignore entries in /etc/exports and uses command line arguments.
-u : un-export one or more directories
-o : specify client options on command line

8. Restart the NFS service:

# systemctl restart nfs-server

Configuring NFS client

1. Install the required nfs packages if not already installed on the server :

# rpm -qa | grep nfs-utils
# yum install nfs-utils

2. Use the mount command to mount exported file systems. Syntax for the command:

 mount -t nfs -o options host:/remote/export /local/directory

Eample :

# mount -t nfs -o ro,nosuid remote_host:/home /remote_home

This example does the following:
– It mounts /home from remote host (remote_host) on local mount point /remote_home.
– File system is mounted read-only and users are prevented from running a setuid program (-o ro,nosuid options).

3. Update /etc/fstab to mount NFS shares at boot time.

# vi /etc/fstab
remote_host:/home 	/remote_home	 nfs 	ro,nosuid 	0 	0

Firewalld services to be active on NFS server

For the NFS server to work, enable the nfs, mountd, and rpc-bind services in the relevant zone in the firewall-config application or using firewall-cmd :

# firewall-cmd --add-service=nfs --zone=internal --permanent
# firewall-cmd --add-service=mountd --zone=internal --permanent
# firewall-cmd --add-service=rpc-bind --zone=internal --permanent
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