"Centralized authentication with LDAP + NFS + Samba (Part II: NFS)"

NFS (Network File System) is an old Unix technology that enables a machine to mount a remote file system. This is desirable for centralized authentication, as the user can access the same home directory no matter which machine he uses.

Server

Install NFS server:

apt-get install nfs-kernel-server

Edit /etc/exports, put in lines such as

/home *.dept.school.edu(rw,no_subtree_check)

to export directories to allow machines on local network have access to /home and its subdirectories.

Start the server:

/etc/init.d/nfs-kernel-server start

If you have a personal firewall running on the machine, you will need to configure it so NFS traffic can be served from this machine. On MEPIS Linux, go to Guarddog->Protocol->Local->Network File System - Sun Microsystems, and check the box, apply; For client, goto the Internet zone, instead of Local zone, check the same box. Since NFS is highly vulunrable for exploitation, you should make sure your whole subnetwork is behind a firewall.

Client

We would like to automatically mount the NFS volume when a user is trying to access it. am-utils, an automounter, will do this. Get and install it:

apt-get install am-utils  

• use NIS: no
• use net map: yes
• use passwd map: no

Edit /etc/am-utils/amd.conf,
Uncomment nfs-proto = udp, for better performance
Add two lines:

[/homes]  
map_name = /etc/am-utils/amd.homes

If user joe's home directory is on machine yoda, we can create a file amd.homes, which contains lines such as:

joe host!=yoda;type:=nfs;rhost:=yoda;rfs:=/home;sublink:=${key};opts:=rw,intr,nosuid,grpid 
host==yoda;type:=link;fs:=/home;sublink:=${key};opts:=rw,intr,nosuid,grpid

Copy this file to all your machines.

Create the mount point:

mkdir /homes

What this does, is to mount a user's home directory on the NFS server (/home/joe) to this NFS client machine, at /homes/joe, whenever /homes/joe is requested. Usually, it happens when user login. Of course, /homes/joe should be this user's default home directory.

ls /homes/joe

If everythings are working, you should be able to see the content of /home/joe on the NFS server.

One more thing, what if the user login to his/her NFS server itself? To avoid a potential problem, the automounter amd should be launched with option -r, so that it will inherent the local file system /home/joe, instead of attempting mount it as a NFS. To achieve this, edit /etc/init.d/am-utils:

append -r to the end of the line :

/etc/sbin/amd -F /etc/am-utils/amd.conf $dnsdomain $AMDARGS

to

/etc/sbin/amd -F /etc/am-utils/amd.conf $dnsdomain $AMDARGS -r

For some system, you may want to comment out this two lines so that amd can start:

echo "$0: please setup your domainname" 1>&2  
exit 1

Now restart amd:

/etc/init.d/am-utils restart

===============
Debian package used
===============
Server:
nfs-kernel-server 1:1.0.6-3.1

Client:
am-utils 6.0.9-3.1