How to solve this NFS unmunt problem?

Question

I have working NFS (Networking File Sharing). It's server path will be mounted, but attempts to use umount are not working. It is getting some error.

$ sudo umount /nfs_server/    
/nfs_server was not found in /proc/mounts    
/nfs_server was not found in /proc/mounts

How can I solve this?

Solution

If the entry is not in /proc/mounts then I suspect your umount was in fact successful. When you attempt to run it again, you'll get the above messages from umount.

You can confirm what you have mounted using the mount command:

$ mount
proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)
sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,relatime,seclabel)
devtmpfs on /dev type devtmpfs (rw,nosuid,seclabel,size=3977672k,nr_inodes=994418,mode=755)
securityfs on /sys/kernel/security type securityfs (rw,nosuid,nodev,noexec,relatime)
selinuxfs on /sys/fs/selinux type selinuxfs (rw,relatime)

Even after unmounting a mount, the directory /nfs_server/ will persist. This is normal behavior, however the contents of the directory will be showing the contents from the system where the mount and umount commands were being run.

NOTE: When the mount is actively engaged from the NFS server, the contents of this directory will be supplied by that server instead.

Comments

[YoloTats.com]

How did you mount /nfs_server/? If there is no entry in /proc/mounts is should be not mounted (anymore).

[slm]

What does the output of mount show?

[S edwards]

you answer your own quesiton, but even your answer is unclear

[FeepingCreature]

This is a genuine issue. Compare bugs.launchpad.net/ubuntu/+source/nfs-utils/+bug/974374 ; the description in the question is entirely accurate. (What's happening is /etc/mtab has a different format for the mount than /proc/mounts.)