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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


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