5 Unix / Linux RPC Mountd Command Examples

rpc.mountd is the server daemon for the NFS mount.

When a remote NFS client is trying to access a file system on the NFS server where mountd is running, this daemon will check the access control in the export table to determine whether to give access to the remote NFS client or not.

rpc.mountd is part of nfs-utils package. You should install it if you don’t have it, using yum install nfs-utils.

The options to mountd can be passed from the command line, or you can use /etc/sysconfig/nfs file which will be used by the /etc/rc.d/init.d/nfs program during startup.

For every successful mount, rpc.mountd adds an entry to the /var/lib/nfs/rmtab file. When it receives the unmount request, it will remove the corresponding enbtry from this rmtab file.

The following is an example of this rmtab file.

# cat /var/lib/nfs/rmtab

1. Change State Directory Path

By default, mountd places all the state information in the /var/lib/nfs directory. If you want to change this to a different location, use -s option as shown below.

# rpc.mountd -s /var/lib/mountd

# rpc.mountd --state-directory-path /var/lib/mountd

As you see below, the following are some of the information that are stored in this directory this rpc.mountd program.

# ls -l /var/lib/nfs
total 32
-rw-r--r-- 1 root    root     366 Aug 22  2011 etab
-rw-r--r-- 1 root    root     454 May  6 09:47 rmtab
drwxr-xr-x 7 root    root       0 Feb 23  2011 rpc_pipefs
drwx------ 4 rpcuser rpcuser 4096 May 18  2010 statd
-rw------- 1 root    root       0 Jan 21  2009 state
drwxr-xr-x 2 root    root    4096 Jan 21  2009 v4recovery
-rw-r--r-- 1 root    root       0 Jan 21  2009 xtab

2. Use hostname of Clients in RMTAB

If you use -r (stands for reverse lookup) option during startup, this will do a reverse lookup on the ipaddress and display the hostname instead of the ip-address that is shown above in the rmtab output.

Please note that enabling this option is not preferred in certain situations, at it will be slow to do reverse lookup of ip-address to get their hostnames. So, be careful if you decide to enable this option.

# rpc.mountd -r

# rpc.mountd --reverse-lookup

3. Increase Number of Threads

Option -t will increase the number of threads. By default, it starts 1 thread. But, if you are running a high volume NFS server which gets several hundred NFS mount request every second, you can increase the threads.

The following example, increases the mountd threads to 5.

# rpc.mountd -t 5

# rpc.mountd --num-threads=5

4. Enable Debugging Levels

mountd program offers these debugging types: all, auth, call, general, parse

You can specify one of this using -d option as shown below. This is helpful when you want to debug some issues with the NFS.

# rpc.mountd -d all

# rpc.mountd --debug all

5. Restrict NFS Version

By default, mountd supports NFS version 2, 3 and 4. If you want to restrict some of the NFS version, you can use the -N option.

The following example restricts NFS version 4.

# rpc.mountd -N 4

# rpc.mountd --no-nfs-version 4