How to enable NFS on the Synology Server

This is a guide on how to enable the NFS capabilities of the Synology product.
This procedure is aimed for users who are experienced with Telnet and the Linux Operating System
Please note that improper manipulation or modification of the Synology server may result in machine malfunction or loss of data.
Please read the General Disclaimer before modifying the Synology product.

Acquire Files

Please make sure that the Synology product has firmware 2.0.3 - 0518 or above, along with the Telnet service or SSH Service enabled.
Both files can be found here.

Instructions for the NFS Server

Telnet into the Synology product and perform the following

Enabling Service

With DSM-5.1 it's already there.

cd /usr/syno/etc/rc.sysv
mv S83nfsd.sh.sample S83****.sh
reboot (or /usr/syno/etc/rc.d/S83****.sh start)
vi /etc/exports 

Note: * needs to be replaced with a number

Note, in newer versions (DSM4), the /usr/syno/etc/rc.d/S83nfsd.sh will already exist. If you try to "start" it, you will get a message telling you that "NFS server is not enabled. Skip..."

You'll need to edit the /etc/synoinfo.conf file and add runnfs="yes". Then you'll be able to run /usr/syno/etc/rc.d/S83nfsd.sh start

Exports file

In the exports file, add the following line

/directory/to/export ip.of.NFS.client(ro,root_squash,no_subtree_check)

Save the export file

Check if the file /var/lib/nfs/rmtab does exist, if not, then run the following command

touch /var/lib/nfs/rmtab

Now perform the following command

cd /
/usr/sbin/exportfs -a

Testing

Look at /var/log/messages to check whether the settings are ok with your Synology product

Instructions for Linux NFS Client

On your NFS client, perform the following to mount the NFS Server share

mount IP.of.NFS.Server:/directory/to/export /volume1/local/share/folder

Note: /volume1/local/share/folder must exist locally, otherwise the mount will fail

Important: NFS on the Synology Server is case-insensitive (as of November 8, 2008; this may change in a later firmware version). This means if you perform backups by (say) rsync, and the source directory contains files named "Foo" and "foo", the destination directory will contain only one of these files, as "Foo" ovewrites "foo" case-insensitively. This behavior happens silently. Update: DSM is case-sensitive over NFS since DSM 2.1

Notes

The NFS Service is disabled after every firmware upgrade.
The NFS mount is not shown in the web interface
Files saved on the Synology server are case-insensitive.
Supported versions:

NFS 2.0

NFS 3.0

NFS 4.0

MTU Jumbo frames

For some NFS clients (eg. TViX 6500/7000), errors are reported if jumbo frames are enabled. Mounting the NFS is possible: try disabling the jumbo frames setting in the Synology Disk Station Manager -> system -> network.

Additional Resources

Synology NFS Forum Room
The /etc/exports file
Mounting NFS File Systems
Windows Services for UNIX 3.5 Fast Setup Guide
Export Filesystem as NFS