Re: Advise on backing up files in Etch.

[Hendrik Boom <hendrik@topoi.pooq.com>]

On Mon, 14 May 2007 11:12:09 -0400, Roberto C. Sánchez wrote:

> On Mon, May 14, 2007 at 02:08:56PM +0200, Dan H wrote:
>> On Sun, 13 May 2007 20:56:21 -0400
>> Roberto C. Sánchez <roberto@connexer.com> wrote:
>> 
>> > Good point.  What I like about the rsync snapshots is that I can
>> > "browse" back in time.  In my case, I always have hourly snapshots
>> > going back four hours, daily snapshots going back four days and weekly
>> > snapshots going back four weeks.  That works out rather nicely in that
>> > it is trivial for me to compare files across snapshots.
>> 
>> That sounds nice but how does it work? I only use rsync to keep exact
>> mirrors of directory trees in sync, but have never heard about the
>> history thingy.
>> 
> If you read "Easy Automated Snapshot-Style Backupse with Rsync" [0],
> it will walk you through the process of setting up rsync to use
> hardlinks to create the snapshots.  That is, you have a "master" backup,
> which is always the most recent (one of the tweaks that I made was to
> use systemimager instead of raw rsync to create that image).  You then
> use rsync to create hardlinks in such a way that only the changed files
> take up additional space.  For example, with a server that has about 5
> GB of space used up (it is a small machine), I can backup the four
> hourly, four daily and four weekly snapshots in a total of about 10 GB
> (instead of the 60 GB that would be required if every image were created
> fresh each time).  That also means that only the first image takes a
> long time to create.  After that, the other images are only the
> differences between the current state and the most recent image.

rdiff-backup was *designed* to do this kind of incremental backup.  Here's
how I back up one of my partitions onto a removable USB hard drive: After
mounting and such, 

rdiff-backup --exclude-other-filesystems --preserve-numerical-ids /farhome /usbackup/backup-by-rdiff/farhome

It only copies what's changed, and it uses reverse differences (insteaf
of hard links) to keep old versions alive, in case I ever need to see them
again.

-- hendrik