Re: [rdiff-backup-users] Restoring to an archive, i.e. making a snapshot

[Andrew Ferguson]

On Jun 18, 2008, at 4:51 AM, Patrick Nagel wrote:

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> Hi,
>
> David Sickmiller wrote on 2008-06-07:
> | I'm using rdiff-backup to run a nightly backup across the Internet  
> from
> | a production server to a backup server.  I'd like to be able to  
> produce
> | monthly snapshots and save them on removable media.  It'd really be
> | great if I could make these snapshots on the backup server, generate
> | them from past revisions, and keep all the meta data.
> |
> | I think I can generate an archive of the current mirror just by  
> making a
> | tar file of it, although I'm not sure if that preserves the meta  
> data.
> | I know it's possible to restore an old revision from rdiff-backup  
> to a
> | regular filesystem, but I don't believe one can "restore" into a  
> file.
> | (It's possible to use FUSE to mount a tar file, but the file  
> ownership
> | and permissions don't work.)  I've been searching online but haven't
> | found much to fit this need.  I find this a bit surprising... am I
> | mistaken to think I want this functionality?
>
> I'm looking for the exact same thing - did you get any useful  
> response? Or did
> you come up with an idea?

If you tar up the current mirror, the rdiff-backup-data, but NOT the  
rdiff-backup-data/increments dir, you will be able to restore the  
current mirror exactly by using rdiff-backup. You could even exclude  
the old files in the rdiff-backup-data dir (they are all time-stamped).

The metadata is all stored in the rdiff-backup-data/mirror_metadata.*  
files. rdiff-backup attempts to apply the metadata to the mirror as  
well, but the mirror_metadata files are the complete record. The most  
recent file is a ".snapshot", and then there are ".diff" files to go  
back to previous mirrors. To save time during restore and guard  
against corruption, rdiff-backup again stores a .snapshot every 10  
increments.

rdiff-backup stores the mirror in "reverse diff" format. That is, the  
contents of the mirror are always the most recent backup, and the  
rdiff-backup-data/increments/ dir stores reverse diffs to go back in  
time. By not keeping those snapshots, you only lose the ability to  
restore timepoints previous to the snapshot. Of course, if you have  
enough space to store the increments as well, there's no downside.  
They are stored compressed, so it's worth checking how big the  
directory is.


Regarding the restore to a FUSE-mounted tar, maybe there's an option  
analogous to tar's --preserve-permissions to do what you want?


Andrew