"That which is overdesigned, too highly specific, anticipates outcome; the anticipation of outcome guarantees, if not failure, the absence of grace."
-- William Gibson, All Tomorrow's Parties
Learn something new everyday.

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).

January 27, 2005 2:54 PM

Adam O. just brought up the point that gzip keeps track of filedate information, etc, and *that* would alter the digest.


Posted by: bda at January 27, 2005 6:56 PM
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