Setting Up An NFS Server And Client On Scientific Linux 6.3

This guide explains how to set up an NFS server and an NFS client on Scientific Linux 6.3. NFS stands for Network File System; through NFS, a client can access (read, write) a remote share on an NFS server as if it was on the local hard disk.

 

1 Preliminary Note

I'm using two Scientific Linux 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 Scientific Linux 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/vg_server2-LogVol00
                      9.7G  1.7G  7.5G  18% /
tmpfs                 499M     0  499M   0% /dev/shm
/dev/sda1             504M   39M  440M   9% /boot
192.168.0.100:/home   9.7G  1.7G  7.5G  19% /mnt/nfs/home
192.168.0.100:/var/nfs
                      9.7G  1.7G  7.5G  19% /mnt/nfs/var/nfs
[root@client ~]#

and

mount
[root@client ~]# mount
/dev/mapper/vg_server2-LogVol00 on / type ext4 (rw)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
devpts on /dev/pts type devpts (rw,gid=5,mode=620)
tmpfs on /dev/shm type tmpfs (rw)
/dev/sda1 on /boot type ext4 (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,vers=4,addr=192.168.0.100,clientaddr=192.168.0.101)
192.168.0.100:/var/nfs on /mnt/nfs/var/nfs type nfs (rw,vers=4,addr=192.168.0.100,clientaddr=192.168.0.101)
[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 0
-rw-r--r-- 1 root root 0 Dec 11 16:58 test.txt
[root@server ~]#
ls -l /var/nfs
[root@server ~]# ls -l /var/nfs
total 0
-rw-r--r-- 1 nfsnobody nfsnobody 0 Dec 11 16:58 test.txt
[root@server ~]#

(Please note the different ownerships of the test files: the /home NFS share gets accessed as root, therefore /home/test.txt is owned by root; the /var/nfs share gets accessed as nobody/65534, therefore /var/nfs/test.txt is owned by 65534.)

 

6 Mounting NFS Shares At Boot Time

Instead of mounting the NFS shares manually on the client, you could modify /etc/fstab so that the NFS shares get mounted automatically when the client boots.

client:

Open /etc/fstab and append the following lines:

vi /etc/fstab
[...]
192.168.0.100:/home  /mnt/nfs/home   nfs      rw,sync,hard,intr  0     0
192.168.0.100:/var/nfs  /mnt/nfs/var/nfs   nfs      rw,sync,hard,intr  0     0

Instead of rw,sync,hard,intr you can use different mount options. To learn more about available options, take a look at

man nfs

To test if your modified /etc/fstab is working, reboot the client:

reboot

After the reboot, you should find the two NFS shares in the outputs of

df -h
[root@client ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/vg_server2-LogVol00
                      9.7G  1.7G  7.5G  18% /
tmpfs                 499M     0  499M   0% /dev/shm
/dev/sda1             504M   39M  440M   9% /boot
192.168.0.100:/home   9.7G  1.7G  7.5G  19% /mnt/nfs/home
192.168.0.100:/var/nfs
                      9.7G  1.7G  7.5G  19% /mnt/nfs/var/nfs
[root@client ~]#

and

mount
[root@client ~]# mount
/dev/mapper/vg_server2-LogVol00 on / type ext4 (rw)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
devpts on /dev/pts type devpts (rw,gid=5,mode=620)
tmpfs on /dev/shm type tmpfs (rw)
/dev/sda1 on /boot type ext4 (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,sync,hard,intr,vers=4,addr=192.168.0.100,clientaddr=192.168.0.101)
192.168.0.100:/var/nfs on /mnt/nfs/var/nfs type nfs (rw,sync,hard,intr,vers=4,addr=192.168.0.100,clientaddr=192.168.0.101)
[root@client ~]#

 

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