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This page will show you how to recover data from a corrupted .tar.bz2 file,
and NOT from a .tar.gz file, since gzip cant do anything with corrupted archives,
it will just leave you despaired, sad, and lonely.
we'll assume you have an archive called "archive.tar.bz2", for which you want:

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None. You can't fix archives with ropes, nor with guns.
Instead, we'll unleash the power of Bzip2 and its builtin Blockwise CRC checks.
Note: The next step will generate A LOT of files.
You might want to create a folder dedicated to that purpose, and copy your archive.tar.bz2 in it.
Let's assume you did that, and that you called that folder recovery/.

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cd into recovery.
Here, we'll use the magic bzip2recover command. Hey, but what's that bzip2recover command. Hmmm.
Bzip2 compressed file are divided into blocks (each block being 100k, 200k, ..., 900k bytes big,
depending on what compression options you used - default is 900k).
What bzip2recover does, is splitting a bzip2 archive into many smaller
bzip2 archives (one per block, actually). That's why it's generating soooo many small files.
So, here we go:

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(this actually parses the output of bzip2 -t to extract only files which don't end up with a candid "ok" -

• guess what, corrupted files don't generate this kind of candid output )

Ouch, i've got corrupted blocks. What should I do with that ?

Note: We are here restoring from a file with only 1 corrupted block. The process would be the same
if you had 15 corrupted blocks, but you had to restore from begining of file to first corrupted block,
then from 1st corrupted block to 2nd, then from 2nd to 3d, ..., and finally
from 15th to the end of file. Did you get it ? I'm sure you did.
Let's focus on the recovery process, now.

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Ok, cd into recovery1.
Here, we have the beginning of a tar file, nothing's corrupted, but the tar file is not complete.
Right. That makes things easy.
We will just bunzip all the small archives into one recovery1.tar file:

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recovery2 !! cd ../recovery2
Hmmmm trying the same method as above fails. Why that ? Because tar sux. Yes, it does.
It does not manage to find a correct header right at the start of the file, and so, fails.
Creepy, huh ? But we are smarter than Tar, and there's not much that a little of Perl Magic can't solve.
First, let's have our bzip2 small archives bunziped into a "failing" tar.

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As I told you right before, a tar tf recovery2_failing.tar would.... fail
What we would need to fix it, is having our recovery2_failing.tar
starting at from the begining of a clean header block.
A simple but efficient perl script will help us to make our way out:

*findtarheader.pl

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\#\!/usr/bin/perl \-w
use strict;
# 99.9% of all credits for this script go
# to Tore Skjellnes <torsk@elkraft.ntnu.no>
# who is the originator.

my $tarfile;
my $c;
my $hit;
my $header;
# if you don't get any results, outcomment the line below and
# decomment the line below the it and retry
my @src = (ord('u'),ord('s'),ord('t'),ord('a'),ord('r'),ord(" "), ord(" "),0);
\#my @src = (ord('u'),ord('s'),ord('t'),ord('a'),ord('r'),0,ord('0'),ord('0'));

die "No tar file given on command line" if $#ARGV \!= 0;

$tarfile = $ARGV[0];

open(IN,$tarfile) or die "Could not open `$tarfile': $\!";

$hit = 0;
$\| = 1;
seek(IN,257,0) or die "Could not seek forward 257 characters in `$tarfile': $\!";
while (read(IN,$c,1) == 1)
{     ($hit = 0, next) unless (ord($c) == $src[$hit]);     $hit = $hit + 1;     ( print "hit: $hit", next ) unless $hit > $#src;       # we have a probable header at (pos - 265)!     my $pos = tell(IN) - 265;     seek(IN,$pos,0) 	or (warn "Could not seek to position $pos in `$tarfile': $!", next);      (read(IN,$header,512) == 512) 	or (warn "Could not read 512 byte header at position $pos in `$tarfile': $!", seek(IN,$pos+265,0),next);      my ($name, $mode, $uid, $gid, $size, $mtime, $chksum, $typeflag, 	$linkname, $magic, $version, $uname, $gname, 	$devmajor, $devminor, $prefix) 	= unpack ("Z100a8a8a8Z12a12a8a1a100a6a2a32a32a8a8Z155", $header);     $size = int $size;     printf("%s:%s:%s:%s\n",$tarfile,($pos+1),$name,$size);      $hit = 0; }
close(IN) or warn "Error closing `$tarfile': $\!";

Yeah, copy/paste and save it. chmod +x on it.
Now, to find the first clean tar header on recovery2_failing.tar, do the following:

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Beside the file name "naked_girls/pamela.jpg", which obviously shows
that the tar file is the backup of Bharathy's Home directory, have a look
at the second field of the output:
17185 : this is the offset of the clean tar header, from the begining of the file.

Good ! Now we have the offset of a clean Tar Header !!
We will be able to recover everything in the tar file starting from that file !
Wooohhhoooooo .

To do so, do the following :

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Well, right, you did it.
We can get something out of it.
For instance, thou shall not use gzip compressed archives for relatively critical stuffs,
because if it ever gets corrupted, well, it's just lost. Sad story, huh ?
Second thing, tar archives are quite fine with data corrupting, at least,
they are better than gzipped files.
Here, we could restore everything from a .tar.bz2 file, EXCEPT what was
within the corrupted bzip block, and everything until the first clean header
after the corrupted block. To sum it up: we lost one block, and any file with
either its header or a part of the body in that block.
If you are saving critical stuff, you could tell BZip2 to use 100kb block-size.
If your archive gets corrupted, you loose a multiple of 100kb,
against a multiple of 900kb if you use 900kb block-size,
which could actually make a BIG difference!