[Gllug] following up to Tushar's backup talk

Philip Hands phil at hands.com
Sun Nov 12 11:39:26 UTC 2006


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Pete Ryland wrote:
> On 12/11/06, Philip Hands <phil at hands.com> wrote:
>> Just thought I'd mention BackupPC:
>>
>>   http://backuppc.sourceforge.net/
> 
> That looks very nice.  An explanation of the cp -al and rsync trick
> can be found here:
> 
> http://www.mikerubel.org/computers/rsync_snapshots/#Incremental

N.B. the mention of the --link-dest option which makes the cp -al step
unnecessary.

Also, he's not mentioning the -H or --hard-links option that should be used
for this sort of thing.  This option ensures that things that are
hard-links in the source directory remain so in the destination, so if you
leave this out then things like gzip, which is hard linked to gunzip,
uncompress & zcat will end up taking 4 times the space needed in the
resulting backup.

That reminds me of one of the features of BackupPC that's not immediately
obvious -- because it has it's own way of tracking hard links that existed
in the source, it can cheerfully hard link things that happened to be the
same without losing the fact that they were really separate files in the
original, so you don't end up with a restored system with all the empty
files hard-linked together (which could be somewhat embarrassing ;-)

Cheers, Phil.
- --
P.S. I'll Cc: Mike Rubel (the Author of that page) in so that he can get
the --hard-links hint
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