FreeBSD: Forcefully unmount a disk partition to get rid of device busy error

by on January 27, 2006 · 1 comment· LAST UPDATED August 28, 2006


Under FreeBSD if you get error device busy while unmounting file system then you can forcefully unmount a disk partition or mount point. You can pass -f option to mount command. It forces the read/write mount of an unclean file system. Suppose you would like to unmount /cdrom forcefully then type command (login as a root user use su or sudo command):

# umount -f /cdrom


  • -f : Forces umount to unmount a disk partition or mounted system
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{ 1 comment… read it below or add one }

1 Rick November 14, 2009 at 9:26 am

Before you do this you should always check what process is keeping your device busy:

Install “lsof” from ports and run:

#> lsof /dev/

This will output a list of users and processes using this device. Then kill one by one and try to unmount again. If no process is using it but you still get the error use the command in this hint above.


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