[ILUG] faq: how to umount a cdrom without rebooting?

[Niall O Broin]

On 23 Nov 2006, at 13:36, Conor McDermottroe wrote:

> On Thu, 2006-11-23 at 11:14 +0000, Niall O Broin wrote:
>> Other than that, it's reboot time. I've had this happen before. I
>> want a new switch added to umount to mean  unmount it NOW and fuck
>> the begrudgers
>
> umount -f doesn't do that for you?

Not always, no. That's specifically for umounting a filesystem  
mounted from a now unreachable NFS server. Won't do squat for a cdrom  
held open by a mystery process.

But here's a little hint from my pain, which has caught me twice in  
the last couple of days, making me unnecessarily reboot a remote box  
(not really yet in use, thankfully). Hopefully it might spare  
somebody else.

The filesystem in question was an LVM volume for a Xen domU. I had  
mounted the filsystem and chrooted into it for whatever maintenance  
reason. On leaving the chroot, I could not umount the filesystem -  
got the good old   /mnt/blah is busy message. Fuser and lsof were  
equally silent. The third time this happened, rather than rebooting  
in annoyance, I thought a little harder (amazing how often that  
helps) and then remembered that before going into the chroot I had  
mounted its /proc filesystem like

mount proc-chroot /mnt/blah/proc -t proc -o defaults

so a simple    umount /mnt/blah/proc    was all that was needed.


Niall