This machine had a stale NFS mount. But attempting to unmount gave a rather strange message:
$ umount /mnt/nfs /mnt/nfs was not found in /proc/mountsLet's look at mtab first:
$ mount | grep nfs server:/mnt/export/dir0 on /mnt/nfs type nfs (ro,vers=4,addr=10.0.0.10,clientaddr=10.0.0.30)OK, but why isn't it found in /proc/mounts then?
$ grep nfs /proc/mounts server:/mnt/export/dir0 /mnt/nfs\040(deleted) \ nfs4 ro,nosuid,nodev,noexec,relatime,\ vers=4,rsize=131072,wsize=131072,namlen=255,\ hard,proto=tcp,port=0,timeo=600,retrans=2,\ sec=sys,local_lock=none,clientaddr=10.0.0.30,\ minorversion=0,addr=10.0.0.10 0 0Hah! Somehow the entry in
/proc/mountsgot mangled. OK,
\040is octal for SPACE. But umount(8) still fails:
$ umount /mnt/nfs\ \(deleted\) umount.nfs: /mnt/nfs (deleted): not found umount.nfs: /mnt/nfs (deleted): not foundApparently
umount(8)tried to find the entries from
/etc/mtabbut failed, due to the mismatch of both files. After adding \040(deleted) to the
$ umount /mnt/nfs* umount: /mnt/nfs Stale NFS file handleThe entry got removed from
/etc/mtab, but the mangled entry still shows up in
/proc/mounts. Now all is left is a stale NFS file handle:
$ umount -f /mnt/nfs umount2: Stale NFS file handle umount: /mnt/nfs: Stale NFS file handleSadly, this could only be cured by a reboot :-\
Update: the "
Stale NFS file handle" error is covered quite nicely in this bugreport. According to this report, the error should be a thing of the past since Linux 3.12.