Configurando NFS no Centos

Setting Up An NFS Server And Client On CentOS 6.3

Version 1.0 Author: Falko Timme <ft [at] falkotimme [dot] com> Follow me on Twitter Last edited 12/11/2012

This guide explains how to set up an NFS server and an NFS client on CentOS 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.

I do not issue any guarantee that this will work for you!

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/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 ~]#