NFS mount how to

Scenario

Imagine one source host, for instance host1.example.org, that will export its storage /store with read/write permissions to two target hosts, for instance host2.example.org and host3.example.org.

I like to use for the target folder the following naming convention

/nfs/<source hostname>

Of course, the target folder must exist on target hosts and it is assumed that there is a route from source to target.

Source host

Connect to host1.example.org, that is our source host.

NFS service

First of all, start NFS service

$ /etc/init.d/nfs start

Make sure the NFS service will start at boot.

$ chkconfig nfs on

Export it

Edit file /etc/exports

/store host2.example.org(rw) host3.example.org(rw)

After changing configuration launch

$ exportfs -au
$ exportfs -a

To check you are exporting filesystems, launch

$ exportfs
/store          host2.example.org
/store          host3.example.org

Target host

Connect to host2.example.org, that is one of the target hosts. Then repeat instructions host3.example.org too.

Mount it

Edit /etc/fstab

host1.example.org:/store /nfs/host1.example.org nfs _netdev,noatime,nfsvers=3,rsize=8192,wsize=8192,nocto,intr,bg,rw,soft,actimeo=300 0 0

Check that source host is exporting correctly

$ showmount -e host1.example.org
Export list for host1.example.org:
/store host2.example.org,host3.example.org

Finally you can mount launching

$ mount /nfs/host1.example.org

or

$ mount host1.example.org:/store

Don’ t forget a final test, just launch

$ df -h
...
host1.example.org:/store 99G  667M   93G   1% /nfs/host1.example.org

Fix listing

After mount, if I do an ls I see something like

$ ls -l /nfs/host1.example.org/

drwx------ 4 15111 15110  4096 Mar 11 18:23 dir1
drwx------ 3 15112 15110  4096 Mar 10 18:06 dir2
drwx------ 3 15109 15110  4096 Mar 10 16:23 dir3

I see ids instead of usernames. In the source host I have these entries in the /etc/passwd

user1:x:15109:15110::/home/user1:/bin/bash
user2:x:15111:15110::/home/user2:/bin/bash
user3:x:15112:15110::/home/user3:/bin/bash

Be consistent: keep the same userid on every host.

In this case, I don’t want users can login on target hosts so, I change home and shell entries to /var/tmp/:/sbin/nologin.

So in /etc/passwd on target hosts I have

user1:x:15109:15110::/var/tmp:/sbin/nologin
user2:x:15111:15110::/var/tmp:/sbin/nologin
user3:x:15112:15110::/var/tmp:/sbin/nologin

Now I can see

$ ls -l /nfs/host1.example.org/

drwx------ 4 user1   15110  4096 Mar 11 18:23 dir1
drwx------ 3 user2   15110  4096 Mar 10 18:06 dir2
drwx------ 3 user3   15110  4096 Mar 10 16:23 dir3

Yep, the same concept applies to group ids. I need to add this row on /etc/group on target hosts

grp1:x:15110:user1,user2,user3

Et voilà! Listing is fixed

$ ls -l /nfs/host1.example.org/

drwx------ 5 user1   grp1  4096 Mar 21 10:05 dir1
drwx------ 3 user2   grp1  4096 Mar 10 18:06 dir2
drwx------ 3 user3   grp1  4096 Mar 10 16:23 dir3