Why do the md5 hashes of two tarballs of the same file differ?
tar czf outfile infiles is equivalent to
tar cf - infiles | gzip > outfileThe reason the files are different is because gzip puts its input filename and modification time into the compressed file. When the input is a pipe, it uses an empty string as the filename and the current time as the modification time.
But it also has a --no-name option, which tells it not to put the name and timestamp into the file. So if you write the expanded command explicitly, instead of using the -z option to tar, you can make use of this option.
tar cf - testfile | gzip --no-name > a.tar.gztar cf - testfile | gzip --no-name > b.tar.gzI tested this on OS X 10.6.8 and it works.
For MacOS:
In man tar we can look at --options section and there we will find !timestamp option, which will exclude timestamp from our gzip archive. Usage:
tar --options '!timestamp' -cvzf archive.tgz filenameIt will produce same md5 sum for same files with same names