Unreachable Remote File Systems

Linux Tutorials - Herong's Tutorial Examples

∟Unreachable Remote File Systems

This section provides a tutorial example on how to resolve the unreachable remote file system problem, which causes all related commands to hang, using the lazy un-mount command 'umount -l'.

Sometimes, a file system mounted from a remote server may become unreachable. This will cause any command that uses the remote file system to hang with no way to break it.

1. "df" command hangs if a remote file system is unreachable with no way to break it.

herong$ df
(no response)

Ctr-C
(no response)
...

2. "kill" command is not able to terminate it.

(log in from another session)
herong$ ps -efl | grep "df"
0 D herong   16317 16237  0  80   0 -  1833 smb2_r 11:11 pts/0   df

herong$ kill -9 16317

herong$ ps -efl | grep "df"
0 D herong   16317 16237  0  80   0 -  1833 smb2_r 11:11 pts/0   df

3. Force un-mount command "umount -f" may give you an error:

herong$ mount | grep share
  //192.168.1.100/share on /mnt/share type cifs ...

herong$ sudo umount -f /mnt/share
  umount: /mnt/share: target is busy.

4. Only the Lazy un-mount command may resolve the problem.

herong$ sudo umount -f -l /mnt/share

herong$ mount | grep share
  //192.168.1.100/share on /mnt/share type cifs ...

(3 minutes later)
herong$ mount | grep share
(no output)

herong$ df
(list of remaining file systems)

Note that the lazy un-mount command "umount -l" detaches the remote file system from the file hierarchy now. It may not be able to clean up all references to the un-mounted file system.