NFS on linux

1. Introduction

The Network File System is certainly one of the most widely used network services. Network file system (NFS) is based on the Remote procedure call. It allows the client to automount and therefore, transparently access the remote file systems on the network.

2. Scenario

In this scenario we are going to export the file system from the linuxconfig.org (IP address 10.1.1.200) host and mount it on linuxconfig.local(IP address 10.1.1.100).

3. Prerequisites

At this point, we assume that the NFS service daemon is already installed on your system, including portmap daemon on which NFS setupt depends. Moreover, your system needs to support the NFS file system.

$ cat /proc/filesystems 

NFS daemon should be listening on both standard ports 2049 and portmap on port 111.

Another way to check if NFS is functioning, is to use the rpcinfo command.

# rpcinfo -p 

You should get a response/output similar to one below:

4. Server export file

All NFS server exports need to be defined in /etc/exports file.

4.1. Most common exports options

Here are the most common export techniques and options:

/home/nfs/ 10.1.1.100(rw,sync)	export /home/nfs directory for host with IP 10.1.1.100 with read, write permissions, and synchronized mode
/home/nfs/ 10.1.1.0/24(ro,sync)	export /home/nfs directory for network 10.1.1.0 netmask 255.255.255.0 with read only permissions and synchronized mode
/home/nfs/ 10.1.1.100(rw,sync) 10.1.1.10(ro,sync)	export /home/nfs directory for host with IP 10.1.1.100 with read, write permissions, synchronized mode, and also export /home/nfs directory for hosts with IP 10.1.1.10 with read only permissions and synchronized mode
/home/nfs/ 10.1.1.100(rw,sync,no_root_squash)	export /home/nfs directory for host with IP 10.1.1.100 with read, write permissions, synchronized mode and the remote root user will be treated as a root and will be able to change any file and directory.
/home/nfs/ *(ro,sync)	export /home/nfs directory for any host with a read only permission and synchronized mode
/home/nfs/ *.linuxconfig.org(ro,sync)	export /home/nfs directory for any host within linuxconfig.org domain with a read only permission and synchronized mode
/home/nfs/ foobar(rw,sync)	export /home/nfs directory for hostname foobar with read, write permissions and synchronized mode

4.2. Edit exports file

Open up your favorite text editor, for example, vim and edit /etc/exports file and add line /home/nfs/ *(ro,sync) to export /home/nfs directory for any host with read only permissions.

Be sure that the directory you export by NFS exists. You can also create a file inside the /home/nfs directory which will help you troubleshoot once you mount this file system remotely.

# touch /home/nfs/test_file 

4.3. Restart NFS daemon

Once you edit /etc/exports file you need to restart NFS daemon to apply changes in the /etc/exports file. Depending on your Linux distribution, the restarting of NFS may differ. Debian users:

# /etc/init.d/nfs-kernel-server restart 

Redhat users

# /etc/init.d/nfs restart 

If you later decide to add more NFS exports to the /etc/exports file, you will need to either restart NFS daemon or run command exportfs:

# exportfs -ra 

5. Mount remote file system on client

First we need to create a mount point:

# mkdir /home/nfs_local 

If you are sure that the NFS client and mount point are ready, you can run the mount command to mount exported NFS remote file system:

# mount 10.1.1.200:/home/nfs /home/nfs_local 

In case that you need to specify a type of the filesystem you can do this by:

# mount -t nfs 10.1.1.200:/home/nfs /home/nfs_local 

You may get error message

mount: mount to NFS server failed: timed out (retrying). 

This may mean that your server supports higher versions of nfs and therefore you need to pass one extra argument to your nfs client. In this example we use nfs version 3:

# mount -t nfs -o nfsvers=3 10.1.1.200:/home/nfs /home/nfs_local 

Now you should be able to see that the file system is mounted. Notice that the mount command reports that the filesystem is mounted as "read and write", although you can see that it provides a "read only" permission.

6. Configure automount

To make this completely transparent to end users, you can automount the NFS file system every time a user boots a PC, or you can also use PAM modules to mount once a user logs in with a proper username and password. In this situation just edit /etc/fstab to mount system automatically during a system boot. You can use your favorite editor and create new line like this:

10.1.1.200:/home/nfs /home/nfs_local/ nfs defaults 0 0 

in /etc/fstab or

# echo "10.1.1.200:/home/nfs /home/nfs_local/ nfs defaults 0 0" >> /etc/fstab