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gzip Recovery Toolkit aka gzrecover
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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 [ -hpsVv ] [-o <filename>] [filename] If no input filename is specific, gzrecover reads from the standard input. By default, gzrecover writes its output to <filename>.recovered. If the original filename ended in .gz, that extension is removed. The default output filename when reading from the standard input is "stdin.recovered". Options include: -o <name> - Sets the output file name -p - Write output to standard output for pipeline support -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 -V - Print version number -o and -p cannot be specified at the same time. Note that gzrecover will run slower than regular gunzip does, but has been significantly inproved in speed since the last release. The more corruption in the file, the more slowly it runs. Running gzrecover on an uncorrupted gzip file should simply uncompress it. However, substituting gzrecover for gunzip on a regular basis is not recommended. Any recovered data should be manually verified for validity. There's no guarantee anything will be recovered 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 that cpio may spew large amounts of error messages to the terminal, and may also take a very long time to run on a file that had lots of corruption. 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! KNOWN ISSUES gzrecover sometimes segfaults on certain files. Neither I nor anyone else has been able to track down the source of this. I am looking for files of reasonable size for which I can replicate this bug on Linux, so if you encounter it with a file that isn't huge, let me know. COPYRIGHT NOTICE gzrecover written by Aaron M. Renn (arenn@urbanophile.com) Copyright (c) 2002-2013 Aaron M. Renn. This code is licensed under the same GNU General Public License v2 (or at your option, any later version). See http://www.gnu.org/licenses/gpl.html
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