[Tfug] disk usage mystery..

[John Gruenenfelder]

On Mon, Mar 5, 2012 at 22:31, JD Rogers <rogersjd at gmail.com> wrote:
>> Yes, when a process exits, in any manner, the OS will take care to
>> close any files it may have had open.  If these files have no further
>> links on the file system, they are deleted.
>
> Hrmm.. that's bad news, because I logged out, switched to a virt term,
> and stopped lightdm... still full disk and what I thought were all the
> likely culprits (firefox, plugin-container, etc) were dead. Not a good
> sign.

If you have the time, I would suggest rebooting (or using telinit to
switch) into a single user run level.  Then you should just have the
kernel, init, and your shell running.  If it is *still* leaking, then
it seems that perhaps you have a kernel bug?

> Well, lsof alo reports size.. I'm currently down about 300MB since
> boot, and lsof reportsa few dozen deleted files all less than 300k. So
> I must still be missing something.

This, along with your non-X test, would seem to indicate that regular
open files are not the culprit.  If you can eliminate all other
processes and still get the problem, then a kernel bug seems most
likely.  However, a kernel bug that has an effect on file system usage
yet is fixed by a reboot and *not* an fsck seems unusual at best.

Here's another shot in the dark: if it *is* in fact a kernel file
system bug, then perhaps it is related the the ext4 journal?  I should
think it has a relatively small maximum size, but maybe it is growing
out of control and this data is released by an unmount?  Seems like
you would encounter other effects from this, though.

Another unlikely but possible culprit could be ecryptfs.  You didn't
say if /home (or wherever the encrypted data is stored) is on its own
partition.  If it is sharing space with root, maybe it's using up the
extra space somehow?


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--John Gruenenfelder    Systems Manager, MKS Imaging Technology, LLC.
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