Recovering Corrupt Zip Files

22 points by AshleysBrain 3 days ago

  > recently we had a particularly bad case: a customer sent us an approximately 1 GB project file which was corrupt, for a game already published to Steam, which they'd spent months working on. They told us all their backups were corrupt too... Predictably, WinRAR's repair tool produced a 1 GB ZIP file that contained nothing.

Thirty years of creating and storing zip files on every major and some minor OSes, filesystems, sketchy transfer protocols, and unreliable media make me think that the huge number of issues this company has with corrupted ZIP files has nothing to do with the format or with its customers' bad practices. I think their software might just produce bad zip files.

toast0 - 35 minutes ago

There's tons of marginal hardware out there, and game developers sometimes push hardware pretty hard and may run early drivers, etc.
BatFastard - 41 minutes ago

As the old saying goes, an untested backup is a non backup.

CrendKing - 41 minutes ago

I just tested. 7-Zip is already doing exactly what the author's recovery tool does: if I delete the metadata at the end of the file, it still can open and extract files, while complaining about the harmless "Unexepcet end of data". Further, even if I delete the actual content of the last file, it still can show the directory structure, it just can't extract data of the last file.

andrewshadura - an hour ago

It seems technically possible to create an append-only ZIP writer that would only add files at the end of a ZIP archive behind the existing central directory, and then write a new central directory including the new files (and excluding the deleted files). That might make it more difficult to irrecoverably damage the archive as most of it contents will likely be preserved after e.g. an abrupt loss of power.