Incremental Backups

Chris McKeever techjedi at
Thu Feb 17 18:20:57 GMT 2005

On Thu, 17 Feb 2005 10:02:07 -0800, Wayne Davison <wayned at> wrote:
> On Wed, Feb 16, 2005 at 08:24:54PM -0500, lists at wrote:
> > It seems that this method would not use terribly much space in terms of
> > duplicating files, however I am not sure of the --delete portion
> In your command sequence, you are (properly) moving the existing
> hierarchy of files out of the way and creating a new hierarchy via
> rsync, hard-linking it via --link-dest.  Thus, there is nothing to
> delete (because the destination is empty), so the --delete has no effect
> an can be dropped from the command. 

the delete is used to sync the original with the mirror (nothing with
the hard linking)
what then happens, is when the rsync delete occurs, the hard link is
maintained, and therefore your incremental backup occurs

so the chain goes

hardlink a mirror directory to a new folder
rsync live data to a mirror directory
deleted files between the mirror/live data are then persistant in the
hardlinked daily directories

there is a much better explanation of this in the linux hacks book -
it works amazing, very small file storage difference, and a years
worth f backup available

 What you _don't_ want to do is to
> rsync into an already existing directory of files using --link-dest;
> that can cause rsync to change the mod-time/permissions/ownership of
> existing files that are hard-linked into older days, and that would make
> them inaccurate for the older days.  (Though it would save space.)
> Others have recommended good backup software, which you can check into.
> There are some other links on the Resources page of the rsync web site.
> ..wayne..
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