Gzrt

gzrecover - Recover data from a corrupted gzip file

gzrecover is a program that will attempt to extract any readable data
out of a gzip file that has been corrupted. 

*****************************************************************************
ATTENTION!!!!  99% of "corrupted" gzip archives are caused by transferring
the file via FTP in ASCII mode instead of binary mode.  Please re-transfer
the file in the correct mode first before attempting to recover from a file
you believe is corrupted.
*****************************************************************************

It is highly likely that not all data in the file will be successfully
retrieved.  In the event that the compressed file was a tar archive, the
standard tar program will probably not be able to extract all of the 
files in the recovered file, so you will need to use GNU cpio instead.

For compilation and installation instructions see README.build

USAGE:

gzrecover [ -hsv ] [-o <filename>] <filename> 

By default, gzrecover writes its output to <filename>.recovered.  If the
original filename ended in .gz, that extension is removed.  Options include:

-o <name> - Sets the output file name
-s        - Splits each recovered segment into its own file,
            with numeric suffixes (.1, .2, etc) (UNTESTED)
-h        - Print the help message
-v        - Verbose logging on

Running gzrecover on an uncorrupted gzip file should simply uncompress it.
However, substituting gzrecover for gzip on a regular basis is not
recommended.

Any recovered data should be manually verified for validity. 

RECOVERING TAR FILES

If your .gz file is a tar archive, it is likely the recovered file cannot
be processed by the tar program because tar will choke on any errors in 
the file format.  Fortunately, GNU cpio will extract tar files and will
skip any corrupted bytes.  If you don't have GNU cpio on your system,
you can download it from ftp://ftp.gnu.org/pub/gnu/cpio/cpio-2.6.tar.gz
Note that I have only tested with version 2.5 or higher.

To extract files, use the following cpio options:

cpio -F <filename from gzrecover output> -i -v

Note: I previously had patched the GNU tar sources to enable it to
skip corrupted bytes, but that patch has been discontinued because it
is not needed and was only marginally successful at best.

PUTTING IT ALL TOGETHER

Your file foo.tar.gz is on a tape with bad data.  To recover, copy the
tape file to foo.tar.gz and:

gzrecover foo.tar.gz
cpio -F foo.tar.recovered -i -v

No guarantees, but I hope this helps you as much as it helped me!

COPYRIGHT NOTICE 

gzrecover written by Aaron M. Renn (arenn()urbanophile.com)
Copyright (c) 2002-2006 Aaron M. Renn. 

This code is licensed under the same GNU General Public License v2
(or at your option, any later version) at GNU tar.  See
http://www.gnu.org/licenses/gpl.html