[RndTbl] Roundtable Digest, Vol 132, Issue 9

[Michael Doob]

This exact situation  has happened to me  due to the following scenario:

I rsync parts of my system nightly onto an external esata drive mounted in
the file system. If something hiccups and the drive gets unmounted,
the backup is done onto the root file system at the mount point, and
then when the drive gets remounted the files on the root system are
hidden in just the way just as you described you described. The script
now looks at what is mounted on the file system before rsync runs.

It's obvious once you see it (just like mathematics).

Cheers,
Michael

On 15-12-23 12:00 PM, roundtable-request at muug.mb.ca wrote:
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> Today's Topics:
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>     1. "Missing" disk space (Adam Thompson)
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> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 22 Dec 2015 12:02:05 -0600
> From: Adam Thompson <athompson at avant.ca>
> To: roundtable at muug.mb.ca
> Subject: [RndTbl] "Missing" disk space
> Message-ID:
> 	<CAFGv8b9jCKjwVhRjJLWm7cSWz9GoxQ5ZYO+AE_gCRsU0rhP8Vg at mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> Documenting for posterity, and in case anyone else runs into the same
> problem:
>
>
> I ran into a situation today where df(1) showed me a filesystem that was
> getting pretty full (109GB used out of 146GB), but when I used du(1) to
> find the space hogs, it was only able to locate <30GB of data on the
> partition.
>
> (Hint: it was the root partition.)
>
> The culprit turned out to be 87GB of files "hidden" underneath
> mountpoints.  If you create /mnt/xyz, copy files into /mnt/xyz/*, then
> mount another filesystem (local or remote) at /mnt/xyz, the original files
> are still there, still taking up disk space, but unavailable.
>
> Luckily, this was a Linux system, and I was able to get access to those
> files using a rebind mount:
> - mkdir /tmp/xyz"
> - "mount -o rebind /dev/mapper/root_lv /tmp/xyz"
> - "cd /tmp/xyz/mnt/xyz"
> - "du -sh *"
> ...yup, there's 87GB of files that I *don't* see under /mnt/xyz.
>
> It's pretty obvious that the files were intended to live on a remote
> fileshare, but got copied in at a point in time when the remote filesystem
> wasn't mounted.  Now I'm mv(1)'ing 87GB of data back across to a Windows
> server across a CIFS mount... time to go for lunch, I guess!
>
> [image: Avant logo] *Adam Thompson*
> Senior Systems Administrator
> *voice:* 204.789.9596 x24 | *email:* athompson at avant.ca | *web:* avant.ca
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> End of Roundtable Digest, Vol 132, Issue 9
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-- 
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Michael Doob                    Telephone: (204) 474-9796
Department of Mathematics       Fax: (204) 474-7606
University of Manitoba          email: Michael_Doob at umanitoba.ca
Winnipeg, MB, Canada R3T 2N2
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