Umounting a Busy Drive Revision as of Monday, 21 December 2015 at 02:30 UTC

This is all too common:

 umount: /media/backupdrive: device is busy
 umount: /media/backupdrive: device is busy

Using lsof

You could try lsof to see what’s using the drive. Use the device name
(/dev/sd*) like so:

 lsof | grep sdd

Using fuser

A more ‘proper’ approach is to use fuser:

 [nikhil@example ~]# fuser -m /dev/sdd5
 /dev/sdd5: 5138

So PID 5138 is using the drive. Let’s see what it is:

 [nikhil@example ~]# ps aux | grep 5138
 nikhil 5138 0.2 2.7 219212 56792 ? SLl Feb11 11:25 rsync -avh --exclude-from=/home/nikhil/manifest / /media/backupdrive

Aha! Now if you’re confident that you can kill that job, go ahead and
then try umounting the drive.