Look what I found …

You often gets device busy when you try to umount some filesystem that’s being used by some obscure process.

# umount /var
umount: /var: device is busy
umount: /var: device is busy

This is a way of finding out which processes that occupies your files.:

# fuser -m /dev/xvdb
/dev/xvdb: 1505


Now you have the info so that you  just can ps ”up” the process ID and etiher kill it or stop the service.

Another way I found out the other day is to force an umount, but not with -f but with -l.

This -l paramter will first force the umount of the device and after the unmountuing it will fix the problems with processes accessing the filesystem in the background..SWEET!

umount -l /var

This will do the trick.