How can I recover files from a corrupted .tar.gz archive?

gzip archive corrupt recover
Tom Melluish picture Tom Melluish · Oct 14, 2008 · Viewed 72.2k times · Source

I have a large number of files in a .tar.gz archive. Checking the file type with the command

file SMS.tar.gz

gives the response

gzip compressed data - deflate method , max compression

When I try to extract the archive with gunzip, after a delay I receive the message

gunzip: SMS.tar.gz: unexpected end of file

Is there any way to recover even part of the archive?

Answer

Liudvikas Bukys picture Liudvikas Bukys · Oct 21, 2008

Recovery is possible but it depends on what caused the corruption.

If the file is just truncated, getting some partial result out is not too hard; just run

gunzip < SMS.tar.gz > SMS.tar.partial

which will give some output despite the error at the end.

If the compressed file has large missing blocks, it's basically hopeless after the bad block.

If the compressed file is systematically corrupted in small ways (e.g. transferring the binary file in ASCII mode, which smashes carriage returns and newlines throughout the file), it is possible to recover but requires quite a bit of custom programming, it's really only worth it if you have absolutely no other recourse (no backups) and the data is worth a lot of effort. (I have done it successfully.) I mentioned this scenario in a previous question.

The answers for .zip files differ somewhat, since zip archives have multiple separately-compressed members, so there's more hope (though most commercial tools are rather bogus, they eliminate warnings by patching CRCs, not by recovering good data). But your question was about a .tar.gz file, which is an archive with one big member.

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