How to use autofs to mount NFS shares

Most Linux file systems are mounted at boot and remain mounted while the system is running. This is also true of any remote file systems that have been configured in the fstab file. However, there may be times when you prefer to have a remote file system mount only on demand—for example, to boost performance by reducing network bandwidth usage, or to hide or obfuscate certain directories for security reasons. The package autofs provides this feature. In this article, I'll describe how to get a basic automount configuration up and running.

First, a few assumptions: Assume the NFS server named tree.mydatacenter.net is up and running. Also assume a data directory named ourfiles and two user directories, for Carl and Sarah, are being shared by this server.

A few best practices will make things work a bit better: It is a good idea to use the same user ID for your users on the server and any client workstations where they have an account. Also, your workstations and server should have the same domain name. Checking the relevant configuration files should confirm.

alan@workstation1:~$ sudo getent passwd carl sarah
[sudo] password for alan:
carl:x:1020:1020:Carl,,,:/home/carl:/bin/bash
sarah:x:1021:1021:Sarah,,,:/home/sarah:/bin/bash

alan@workstation1:~$ sudo getent hosts
127.0.0.1       localhost
127.0.1.1       workstation1.mydatacenter.net workstation1
10.10.1.5       tree.mydatacenter.net tree

As you can see, both the client workstation and the NFS server are configured in the hosts file. I’m assuming a basic home or even small office network that might lack proper internal domain name service (i.e., DNS).

Install the packages

You need to install only two packages: nfs-common for NFS client functions, and autofs to provide the automount function.

alan@workstation1:~$ sudo apt-get install nfs-common autofs

You can verify that the autofs files have been placed in the etc directory:

alan@workstation1:~$ cd /etc; ll auto*
-rw-r--r-- 1 root root 12596 Nov 19  2015 autofs.conf
-rw-r--r-- 1 root root   857 Mar 10  2017 auto.master
-rw-r--r-- 1 root root   708 Jul  6  2017 auto.misc
-rwxr-xr-x 1 root root  1039 Nov 19  2015 auto.net*
-rwxr-xr-x 1 root root  2191 Nov 19  2015 auto.smb*
alan@workstation1:/etc$

Configure autofs

Now you need to edit several of these files and add the file auto.home. First, add the following two lines to the file auto.master:

/mnt/tree  /etc/auto.misc
/home/tree  /etc/auto.home

Each line begins with the directory where the NFS shares will be mounted. Go ahead and create those directories:

alan@workstation1:/etc$ sudo mkdir /mnt/tree /home/tree

Second, add the following line to the file auto.misc:

ourfiles        -fstype=nfs     tree:/share/ourfiles

This line instructs autofs to mount the ourfiles share at the location matched in the auto.master file for auto.misc. As shown above, these files will be available in the directory /mnt/tree/ourfiles.

Third, create the file auto.home with the following line:

*               -fstype=nfs     tree:/home/&

This line instructs autofs to mount the users share at the location matched in the auto.master file for auto.home. In this case, Carl and Sarah's files will be available in the directories /home/tree/carl or /home/tree/sarah, respectively. The asterisk (referred to as a wildcard) makes it possible for each user's share to be automatically mounted when they log in. The ampersand also works as a wildcard representing the user's directory on the server side. Their home directory should be mapped accordingly in the passwd file. This doesn’t have to be done if you prefer a local home directory; instead, the user could use this as simple remote storage for specific files.

Finally, restart the autofs daemon so it will recognize and load these configuration file changes.

alan@workstation1:/etc$ sudo service autofs restart

Testing autofs

If you change to one of the directories listed in the file auto.master and run the ls command, you won’t see anything immediately. For example, change directory (cd) to /mnt/tree. At first, the output of ls won’t show anything, but after running cd ourfiles, the ourfiles share directory will be automatically mounted. The cd command will also be executed and you will be placed into the newly mounted directory.

carl@workstation1:~$ cd /mnt/tree
carl@workstation1:/mnt/tree$ ls
carl@workstation1:/mnt/tree$ cd ourfiles
carl@workstation1:/mnt/tree/ourfiles$

To further confirm that things are working, the mount command will display the details of the mounted share.

carl@workstation1:~$ mount
tree:/mnt/share/ourfiles on /mnt/tree/ourfiles type nfs4 (rw,relatime,vers=4.0,rsize=131072,wsize=131072,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,clientaddr=10.10.1.22,local_lock=none,addr=10.10.1.5)

The /home/tree directory will work the same way for Carl and Sarah.

I find it useful to bookmark these directories in my file manager for quicker access.