sshfs device is busy

Question

I mounted a remote file system using sshfs (version 2.8.4)

sshfs -o allow_root joeuser@example.com: ./example

but unmounting it fails

> fusermount -u example
umount: /home/joeuser/example: device is busy.
        (In some cases useful info about processes that use
         the device is found by lsof(8) or fuser(1))

Any ideas as to what might be causing this error and how one might fix it?

Answer 1

Some program is using a file in the filesystem you're trying to unmount. It could be a file opened for reading or writing, a current directory, or a few more obscure cases. It could even be due to a directory on the filesystem being a mount point.

To investigate, run lsof +f -- example. It will tell what the process(es) are using the filesystem. Make your own judgement as to whether to make them close files, kill them, or defer the unmount operation.

Answer 2

I often see "device busy" with sshfs when I have a terminal window open to a directory on the sshfs share. Exiting the terminal or changing directories to a local share then running fusermount -u solves my problems.