Setting Up An NFS Server And Client On CentOS 5.5

1 Preliminary Note

I'm using two CentOS systems here:

• NFS Server: server.example.com, IP address: 192.168.0.100
• NFS Client: client.example.com, IP address: 192.168.0.101

2 Installing NFS

server:

On the NFS server we run:

yum install nfs-utils nfs-utils-lib

Then we create the system startup links for the NFS server and start it:

chkconfig --levels 235 nfs on
/etc/init.d/nfs start 

client:

On the client we can install NFS as follows (this is actually the same as on the server):

yum install nfs-utils nfs-utils-lib

3 Exporting Directories On The Server

server:

I'd like to make the directories /home and /var/nfs accessible to the client; therefore we must "export" them on the server.
When a client accesses an NFS share, this normally happens as the user nobody. Usually the /home directory isn't owned by nobody (and I don't recommend to change its ownership to nobody!), and because we want to read and write on /home, we tell NFS that accesses should be made as root (if our /home share was read-only, this wouldn't be necessary).
The /var/nfs directory doesn't exist, so we can create it and change its ownership; in my tests the user and group nobody both had the ID 99 on both my CentOS test systems (server and client); when I tried to write to /var/nfs from the NFS client, I got a Permission denied error, so I did a chmod 777 /var/nfs so that everyone could write to that directory; writing to /var/nfs from the client worked then, and on the client the files written to /var/nfs appeared to be owned by the user and group nobody, but on the server they were owned by the (nonexistant) user and group with the ID 65534; so I changed ownership of /var/nfs to the user/group 65534 on the server and changed permissions of /var/nfs back to 755, and voilà, the client was allowed to write to /var/nfs:

mkdir /var/nfs
chown 65534:65534 /var/nfs
chmod 755 /var/nfs

Now we must modify /etc/exports where we "export" our NFS shares. We specify /home and /var/nfs as NFS shares and tell NFS to make accesses to /home as root (to learn more about /etc/exports, its format and available options, take a look at

man 5 exports

)

vi /etc/exports

/home 192.168.0.101(rw,sync,no_root_squash,no_subtree_check) /var/nfs 192.168.0.101(rw,sync,no_subtree_check)

(The no_root_squash option makes that /home will be accessed as root.)

Whenever we modify /etc/exports, we must run

exportfs -a

afterwards to make the changes effective.

4 Mounting The NFS Shares On The Client

client:

First we create the directories where we want to mount the NFS shares, e.g.:

mkdir -p /mnt/nfs/home
mkdir -p /mnt/nfs/var/nfs

Afterwards, we can mount them as follows:

mount 192.168.0.100:/home /mnt/nfs/home
mount 192.168.0.100:/var/nfs /mnt/nfs/var/nfs

You should now see the two NFS shares in the outputs of

df -h

[root@client ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
                       28G  2.2G   25G   8% /
/dev/sda1              99M   13M   82M  14% /boot
tmpfs                 250M     0  250M   0% /dev/shm
192.168.0.100:/home    28G  2.6G   25G  10% /mnt/nfs/home
192.168.0.100:/var/nfs
                       28G  2.6G   25G  10% /mnt/nfs/var/nfs
[root@client ~]#

and

mount

[root@client ~]# mount /dev/mapper/VolGroup00-LogVol00 on / type ext3 (rw)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
devpts on /dev/pts type devpts (rw,gid=5,mode=620)
/dev/sda1 on /boot type ext3 (rw)
tmpfs on /dev/shm type tmpfs (rw)
none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw)
sunrpc on /var/lib/nfs/rpc_pipefs type rpc_pipefs (rw)
192.168.0.100:/home on /mnt/nfs/home type nfs (rw,addr=192.168.0.100)
192.168.0.100:/var/nfs on /mnt/nfs/var/nfs type nfs (rw,addr=192.168.0.100)
[root@client ~]#

5 Testing

On the client, you can now try to create test files on the NFS shares:

client:

touch /mnt/nfs/home/test.txt
touch /mnt/nfs/var/nfs/test.txt

Now go to the server and check if you can see both test files:

server:

ls -l /home/

[root@server ~]# ls -l /home/
total 55540
-rw-r--r-- 1 root         root                0 Sep 16 17:30 test.txt
[root@server ~]#