Sharing files via NFS

NFS is a protocol for sharing storage over a network. It has been supported by unix since day . (dot) and I believe now windows even supports it!

In order to share a directory on ubuntu, first install the prerequisites:

sudo apt-get install nfs-kernel-server nfs-common portmap

Then modify the file /etc/exports and specify the folders that are going to be made available to clients, for example:

/media/share 127.0.0.0/24(rw,sync,no_subtree_check,insecure,all_squash,anonuid=1000,anongid=1000)

What does all that mean!??

• /media/share is a directory to export. By default, all directories contained within /media/share will also be available
• 127.0.0.0/24 is the address/netmask of devices that have access to the shares. If you do not care who has access, the wildcard * can be used
• Contained within the parenthesis is a series of options:
• rw – Allow both read and write operations. To allow only read access, use ro instead
• sync – Ensures that changes to files are committed to stable storage, as opposed to async in which a crash can lead to unclean server state and cause data to be lost or corrupted
• no_subtree_check – disables the subtree checking, this is recommended for home directories and others that are mounted rw. This is the default
• insecure – Allow non-default ports for accessing the NFS server. By default, port requests are expected to be on ports less than 1024 (usually by the root user)
• all_squash – Ignore the uid/gid of the connected user (map it to the anonymous user)
• anonuid – Set the uid of the anonymous user. This and anongid option is useful for clients where you might want all the requests to appear to be from a single user
• anongid – Set the gid of the anonymous user

Additional examples can be found in the exports(5) man page.

Once /etc/exports has been modified, restart the NFS server and re-export:

sudo /etc/init.d/nfs-kernel-server restart
sudo exportfs -a

In order to see if the exports are working correctly, run the showmount utility:

showmount -e localhost

Example output:

Export list for localhost:
/media/share 127.0.0.0/24

To mount this new share, run the mount command:

sudo mount localhost:/media/share /mnt

Ensure that the mount is successful, and it can be viewed by either:

mount 
df -h