3 ms·

How do you create a tar archive that "contains absolute paths"?

• 10000truths 2y ago
  The tar file format doesn't prevent you from specifying absolute paths in the archive. It's up to the tool extracting the archive to reject/ignore such paths.
  • vorakl 2y ago
    I asked about options for GNU tar because there is a bit of strange behavior. To add absolute paths to an archive, there is "-P" option, and man says it works only for creating archives: "Don't strip leading slashes from filenames when creating archives". To extract absolute paths from the archive, you need to add the "-C /" option, and although the tool says "tar: Strip leading `/' from member names", it will still extract it in the right place because the paths become relative and -C puts them in the root. However, if you add "-P" during the extraction (which is not mentioned in man), the "strip leading slashes" information disappears. So if this message bothers someone, "tar -C / -xPf file.tar" will cleanly extract absolute paths from the archive ;)
• yjftsjthsd-h 2y ago
  The first field in the tar header is char name[100]; (See https://man.archlinux.org/man/tar.5.en https://man.archlinux.org/man/tar.5.en ) So anything that will write an absolute path there, including literally opening it in a text editor and replacing the path by hand because that whole header is just fixed length ASCII with null terminated strings. (I mean I assume the tar(1) command can do it too but you don't need that, the format is dead simple, if weird.)
  • eichin 2y ago
    It's a good exercise to open one of these files in hexdump or something to get a feel for what's really going on inside... but yeah, GNU tar has -P / --absolute-names to just create them with leading slashes.