Re: Features of dar

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Alexander Skwar wrote:
> Hello.

Hello,

> 
> I'm interested in using Dar for the backup of my server. I haven't 
> yet used Dar and did not find that question answered on the 
> "Featuers"  page at <http://dar.linux.free.fr/doc/Features.html>.

OK, so you give the opportunity to update this page ;-)

> 
> So, here it goes.
> 
> - Can dar show me, which different "versions" of a file have been 
> backed up?
> Example: Suppose you're backing up the /data directory, which 
> contains the file "report.txt". You're doing a backup every day.
> Can dar now easily "tell" me, that the file "/data/reports.txt" 
> exists in the backups with a modification date of, let's say, 
> 2006-10-12, 2006-12-24 and 2007-05-05? Can I then also easily 
> retrieve the file with the modification date of 2006-12-24?

First, each backup contains only one copy of a given file. It is easy to
 known whether a given file is saved or not in an archive (Full /
incremental backup) and to get the 'ls-like' output of the archive
contents thus of that file (some filtering mecanismes are present inside
dar, but you can also pipe dar's output through grep for example). Among
this output figures the last modification date. Thus to answer your
question, you can get the date of modification of a given file contained
in an archive.

Second, as you can guess, you have to would have to list each archive to
be able to find the version the version of a given file in a given
state. As I am a very lazy person and is using dar, I thus developped
dar_manager beside dar.  Dar_manager collects the contents of several
archive which are computed into a so-called 'dar manager database' (aka
DMD). From a DMD dar_manager provide you the list of archive used to
build the current DMD, of course you can ask dar_manager to list you all
the archive where a given file is present, it will provide you the
archive beside last modification dates the file has been saved under in
each particular archive. Last point here, as I am very lazy guy, as I
already said, dar_manager can call dar for you on the necessary archives
 to restore a set of file as they were at a particular date. ;-) you
will not have to call dar, but dar will ask you to provide the slice N
of archive M (M is the name of the archive you have been using). If you
are very lazy like I am, you can also use some simple script that can be
provided to dar thanks to -E option to automatically mount/unmount a DVD
or CD and even eject the CD. The only thing that will remain in your
list of action is to wait for dar's output, read it, and put the CD in
the tray.

> 
> - More or less related to the first question: Can I retrieve a file
> with the "latest version", before it was deleted?

Yep, this is dar_manager behavior when no date is provided.

> Example: We've got the file /data/quotes.txt. It's backed up every
> day. Today we discover that the file is gone. Can I know somehow 
> get the  information from dar when the file last existed?

Yep, absolutely.

> 
> - I suppose the following is possible, but anyway. Suppose you did
> a full backup at the first day of the month. After that, you're
> doing only differentials. So, as of now,you'd have 19 differentials
> (since today is the 20th day of the month). Now you want to restore
> a directory the way it was on the 10th. Can you do a restore to a
> specific  point-in-time? I very much guess so.

Yep, just use dar_manager over a DMD fed by the 20 archives (1 full and
19 differentials) asking to restore the directory at the date that falls
between the 10th and the 11th archive have been done.

There is currently a limitation on the number of entry that the
directory contains which is due to the fact that dar_manager and dar
communicate throught dar's command line, which may be too short in some
case. A new feature is under developement to let them communicate
through an anonymous pipe.

Note that you can remove archives from a DMD as well you can add
archives to it. You don't need to rebuild the DMD each time you recycle
a set of full and differential backup, assuming you rotate your backups
over more than on set.

> 
> Thanks a lot,
> 

You are welcome,

> Alexander Skwar
> 

Regards,
Denis.
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.7 (GNU/Linux)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org

iD8DBQFGe3dopC5CI8gYGlIRApmmAJ9EhgsLx5VAzErk0+g2JeiiyD88EgCcCelM
H4e+19FI9/80AgfDp4JOT34=
=vf5U
-----END PGP SIGNATURE-----

-------------------------------------------------------------------------
This SF.net email is sponsored by DB2 Express
Download DB2 Express C - the FREE version of DB2 express and take
control of your XML. No limits. Just data. Click to get it now.
http://sourceforge.net/powerbar/db2/