[CentOS] Best backup software for linux

Peter Crighton centos at p-cright.demon.co.uk
Mon Nov 6 18:42:01 UTC 2006

On Sun, 5 Nov 2006 14:43:38 -0800 , you wrote:

>Jeff Stacey wrote:
>> On Fri, 2006-03-11 at 10:28 -0800, Bbt Lists wrote:
>>> Mark Schoonover wrote:
>>>>>>>> Maybe this is something I should write up in more detail. The
>>>>>>>> entire system runs on just a couple of shell scripts, rsync, and
>>>>>>>> Perl program to mail out logs....
>>>>>>>> HTH
>>>>>>>> Mark
>A day late, but ran into some problems with blogspot. The article is 
>posted at: http://marks-tech-pages.blogspot.com - titled Linux Based Poor
>Man's SAN.

Bit of a Linux newbie so I may have misunderstood the below (but am
interested in a similar but much smaller scale setup for my home
network) - planning on using tape but this looks more inviting (I
could use tape for long term permanent backup).

You wrote "Hardlinks are key to this backup strategy. Using cp -al
creates hardlinks to files, and this simple command is what does all
the heavy lifting for daily and weekly backups. Wikipedia has a very
good explanation on how hardlinks work. In a nutshell, when there's a
hardlink pointing to a file from the hourly directory, to a file in
the current directory, and that current file gets deleted, all the
links that point to that now deleted current file gets the file data
'pushed' back towards all the links. I'll have to think how to explain
this better."

Do you mean that the hourly files are written when created, the
hardlink for the daily doesn't actually copy the file (simply makes a
link), but if the file is set to be deleted from it's location
(because it's gone from the server) then it is actually moved so that
it still exists in the daily backup  but is removed from the hourly?

Peter Crighton

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