[Dirvish] misuse of chown as root leads to excessive backup usage

Keith Lofstrom keithl at kl-ic.com
Tue Feb 8 12:12:31 PST 2005


I did something silly last night.  On one of my machines, I was
creating a dummy user "samexample" for a demonstration.  I copied
some .* directories over from another user, then, as root, did a
chown -R samexample.samexample .* in the ~samexample directory.
After it didn't come back for a few seconds, I realized it was not
the bad wifi link, but a bad mistake, and stopped it.  But not before
it had changed a bunch of files in ../[otherusers] to ownership 
samexample.samexample .  Well, that was not to hard to fix (annoying,
though). 

As a result, though, about 8GB of files and directories were changed
and re-dated by the OS.  Dirvish/rsync copied all of them to the backup
drive, which was the only way to accomodate the new dates.

So, a warning - anything that touches/redates a lot of files will
cause rsync to consider them changed and move them.  Because the files
now have differing dates between the client and the server, the only
way to make rsync to not move the files is to (1) run with the checksum
flag set, for all backups into the future (this is very slow) or (2) to
restore the dates on the client, somehow.  Since I don't know of a safe
way to restore that dates without risking data, I will just have to live
with 8GB shaved off each of the rotating backup drives.  Sigh.

Let that be a warning - chown as root (and being in a hurry before
a demo) can eat up a LOT of backup disk space.

Keith

-- 
Keith Lofstrom          keithl at keithl.com         Voice (503)-520-1993
KLIC --- Keith Lofstrom Integrated Circuits --- "Your Ideas in Silicon"
Design Contracting in Bipolar and CMOS - Analog, Digital, and Scan ICs


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