How to get the list of clients connected to an NFS server within a local network? [closed]

Question

I have an NFS server with folder permissions as follows. There are 50 clients which need to connect to this server within the same network. I would like to know what's the command to lookup which are the clients accessing this server from the server.

NFS Server configuration file looks like this.

[root@server ~]# cat /etc/exports
/home/guests    *(rw,sync)
/india          *(rw,sync)

Below are the list of shared folders

[root@server ~]# showmount -e
Export list for server.sanith.com:
/india       *
/home/guests *

For testing purpose I have now connected one client to the server. Below output is from the "client2" machine.

[root@client2 ~]# showmount -e 192.168.1.10
Export list for 192.168.1.10:
/india       *
/home/guests *
[root@client2 ~]# mount -t nfs 192.168.1.10:/india /test
[root@client2 ~]# mount
/dev/sda2 on / type ext4 (rw)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
devpts on /dev/pts type devpts (rw,gid=5,mode=620)
tmpfs on /dev/shm type tmpfs (rw,rootcontext="system_u:object_r:tmpfs_t:s0")
/dev/sda1 on /boot type ext4 (rw)
/dev/sda3 on /home type ext4 (rw)
none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw)
gvfs-fuse-daemon on /root/.gvfs type fuse.gvfs-fuse-daemon (rw,nosuid,nodev)
sunrpc on /var/lib/nfs/rpc_pipefs type rpc_pipefs (rw)
192.168.1.10:/india on /test type nfs (rw,vers=4,addr=192.168.1.10,clientaddr=192.168.1.12)

I tried using showmount -a and showmount -d but not sure what am missing which's not list the client machines connected.

[root@server ~]# showmount -a
All mount points on server.sanith.com:
[root@server ~]# man showmount
[root@server ~]# showmount -d
Directories on server.sanith.com:
[root@server ~]# netstat -an | grep 192.168.1.10:2048
[root@server ~]# netstat -an | grep 192.168.1.10:2049
[root@server ~]# cat /var/lib/nfs/rmtab
[root@server ~]#

Note : The firewall is disabled on the server temporarily during this testing. Please advise.

Answer 1

You can find connected NFS clients by running the following on the NFS server:

netstat | grep :nfs

Answer 2

NFS works over both UDP and TCP, only open TCP connections will show in netstat or ss. Also, as a distributed filesystem, it has (historically) had its fair share of problems^PDF (state, cache, locking, notifications, security — some of which have solutions through extra RPC features, e.g. rpc.statd).

On a Linux NFS server (see man rpc.mountd) the client mount/unmount requests are recorded in /var/lib/nfs/rmtab, just like /etc/mtab, sothe answer should be:

cat /var/lib/nfs/rmtab

If it's empty, then you either have a problem with rpc.mountd (so you should check the RPC services running), or all the clients are NFSv4 which doesn't use this feature.

On versions I've checked rmtab is presented as:

10.1.2.0/24:/path/to/export1:0x000...flags
10.1.2.10:/path/to/export1:0x0000...flags
10.1.2.22:/path/to/export1:0x0000...flags
10.1.2.0/24:/path/to/export2:0x000...flags
10.1.2.22:/path/to/export2:0x0000...flags
10.1.2.99:/path/to/export2:0x0000...flags

i.e., each mount point is listed, followed by the clients using it.

Note the caveat in the man page:

However, this file is mostly ornamental. One, the client can continue to use the file handle even after calling rpc.mountd's UMOUNT procedure. And two, if a client reboots without notifying rpc.mountd, a stale entry will remain in rmtab.

The /proc/fs/nfsd/client approach (@Vsevolod Gromov's answer) in newer kernels should be better in this respect, but because it only supports NFSv4 clients which should be better behaved.