unable to umount ... device busy

unable to umount ... device busy

Post by Itai Nahsho » Wed, 28 Aug 2002 07:50:05

Well, sorry for bringing this up here3 but I do not know
of a better forum for this subject...

Working in an environment of multiple Linux systems
(and wildly using NFS and am-utils) I have hit this problem
many times and in some cases I can describe it as "embarrassing".

The problem is that processes that do not really care about their
working directory are standing in the way of umount.
It is most painful when I cannot eject a CD (or other removable
device) and sometimes with NFS mounted directories.

Most guilty programs:
su + the pam patch (as distributed by redhat) there's a process just
  waiting for the shell to exit.
Daemons - should cd to "/" except if there is some other preferred

Related subject and not completely OT: I remember in AIX, umount -f
(forced umount) marked all the open inodes on the device as
STALE and then proceed (and never return EBUSY). Any plans
to implement it also for Linux?

-- Itai

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1. umount: /dev/{device}: device is busy

I seem to be having a weird sporradic problem with umount.  I am
running Linux 0.99PL12 release SLS1.03 on my 486DX/33.  When I mount a
drive - whether it be another harddisk/partition or a floppy - umount
sometimes refuses to let me unmount it, responding with the above
error.  I have to reboot to clear it, and the reboot program notes
that it can't unmount the drive either, but reboots anyway.  (Is that
safe?)  When the system comes back up, the drive is unmounted.

The man pages say that the error is caused by some process using the
files under the mount point or having a wd under the mount point, but
I don't know what processes would be under /mnt (where I typically
mount stuff).

Since it doesn't happen all the time, it's not easy to trace.  Can
someone tell me what's a good way to determine the wd of a process?
Is there anything other than the process-under-mount-point thing that
could be causing the umount problem?  Any help, answers, or
suggestions would be appreciated!

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