Re: losetup -d --force for zombie loop devices?

[Mike Frysinger <vapier@gentoo.org>]

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On Thursday 03 May 2012 10:29:07 Phillip Susi wrote:
> On 5/3/2012 12:43 AM, Mike Frysinger wrote:
> > conversely, having a mount point removed from the perspective of
> > userspace can be useful.  like with tools that stubbornly enumerate all
> > mounts, or attempting to shutdown your system with known unreachable
> > network mounts. you, as the admin, know these things are gone and beyond
> > accessible, so having the ability to remove them all manually and reboot
> > cleanly (w/out ridiculous long retries/timeouts) is a good thing.
> 
> If you want to hide mounts from certain processes, that is what unshare
> is for.  Hiding a mount from all processes does not make sense.  If you
> know a mount is gone and beyond recovery ( like in this loop over nfs
> case, or removed media ), then it should be forcibly unmounted, not
> simply made invisible and doomed to remain a zombie mount until the
> system is rebooted.

in an ideal world, maybe unshare might work.  in the real world, it doesn't.  
you can use it only on *new* processes, not ones that are already running.  
nor can you do `unshare shutdown` and have it work since that simply signals a 
long running init process to initiate a shutdown.

an nfs server goes afk and attempts to `umount` it timeout, as well as many 
desktop programs (like kde io daemons that like to walk available mount 
points) or shutdown processes.  no call to `unshare` will fix this, but 
certainly forcibly removing it with `umount -l` will.
-mike

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