Unix & Linux Stack Exchange is a question and answer site for users of Linux, FreeBSD and other Un*x-like operating systems. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I had a USB drive mounted on /dev/sdb1 and I want to reformat from NTFS to ext3. I did umount -l which unmounted the disk. I deleted the old partition using cfdisk. I ran mkfs.ext3, but got the error:

/dev/sdb1 is apparently in use...

After googling I tried to cat /proc/mounts and found it there:

/dev/sdb1 /media/moviesold 

How do I remove the reference from there? How did it get there? More specifically what can I run to "really umount"?

share|improve this question
up vote 4 down vote accepted

Use umount. You ran umount -l, which specifically tells umount to leave the filesystem mounted until all processes are done with it. You really shouldn't need umount -l most of the time; the only purpose it serves is freeing up the mount point so you can mount something new there while the currently mounted partition is still in use. Now that you've already lazy unmounted it, if you figure out which process still has a file open on the filesystem and close it it will unmount automatically

share|improve this answer
Thanks, I thought the -l meant "force unmount" for some reason. I still cant format but that is a separate question. – cjburkha Feb 13 '13 at 12:33

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.