-- William Gibson, All Tomorrow's Parties
So I'm installing the machine that will replace both hastur and ligur, named ligur Mk II. I'm installing postfix, and when it pulls the tls/ipv6/pf patch, it throws a checksum error. "What the hell," says I, and grab an md5 of the file. Sure enough, it doesn't match the checksum listed in distinfo. So I go check on another box, and sure enough... so then I uncompress the two patches, get digests, and they're the same. I copy the patches to a third machine and diff the "bad" and known good patches. No differences.
Same filesize, same chars, same digest. So I recompress the "good" patch on the working box, and copy it over the new box. Same checksum error.
After a few minutes of screwing around, I think to myself...
[bda@selene]:[~]$ touch foobar ; gzip foobar ; md5 foobar.gz
MD5 (foobar.gz) = 36b0031ef3f51c3ceaa0700d8546de41
[bda@selene]:[~]$ rm foobar.gz; touch foobar ; gzip foobar ; md5 foobar.gz
MD5 (foobar.gz) = 997d552d8d6835a6f2b4ea719ba350d5
Apparently gzip flips bits as part of its compression algo. Useful so you know if a file has been recompressed (which must have happened on the mirror I pulled the patch from originally).
Adam O. just brought up the point that gzip keeps track of filedate information, etc, and *that* would alter the digest.
Duh.Posted by: bda at January 27, 2005 6:56 PM