Linux NFS Troubleshooting
Internal
List Filesystems Exported by a NFS Server
List Filesystems Mounted by a NFS Client
Verbose mount
Try to mount with -v (verbose). For more details see mount.
Useful Commands
showmount
showmount -e
on the server to see what is exported.
rpcinfo
Failures
mount hangs
I've seen cases when trying to mount a filesystem from other machine hangs if nfs is not started on that machine (service nfs start).
mount.nfs: access denied by server while mounting
I've also seen cases when I get the following error message when not using -t nfs, so use -t nfs:
mount.nfs: access denied by server while mounting f01:/opt/shared
mount(2): No such file or directory
mount -v yields:
mount.nfs: trying text-based options 'bg,vers=4,addr=172.31.20.184,clientaddr=172.31.21.24' mount.nfs: mount(2): No such file or directory ...
I get this because I use the wrong exported path in /etc/fstab.
mount(2): No route to host
mount -v yields:
mount -v -t nfs 192.168.1.2:/volume3/dropbox /mnt/tmp mount.nfs: timeout set for Sun Aug 21 00:44:48 2016 mount.nfs: trying text-based options 'vers=4,addr=192.168.1.2,clientaddr=192.168.1.9' mount.nfs: mount(2): No route to host
This error means that the NFS client host is not getting a TCP/IP ACK back from the NFS server.
The problem went away after configuring iptables to allow all outbound traffic (see iptables Service Configuration).
mount(2): Permission denied
mount -v yields:
mount -v -t nfs 192.168.1.4:/volume3/dropbox /mnt/tmp ... mount.nfs: mount(2): Permission denied mount.nfs: access denied by server while mounting 192.168.1.4:/volume3/dropbox
The error is paired with the following on the server-side:
Aug 21 01:35:58 RackStation mountd[11206]: refused mount request from 192.168.1.9 for /volume3/dropbox (/volume3/dropbox): unmatched host
The root cause was the fact 192.168.1.9 was not specifically allowed access in the server's /etc/exports.