In hackish lore, refers to the mutated punchline of an age-old joke
to be found at the bottom of the manual pages of
tunefs8
in the original BSD 4.2 distribution. The joke was
removed in later releases once commercial sites started using 4.2, but
apparently restored on the 4.4BSD tape and in {Net,Free,Open}BSD. Tunefs
relates to the tuning of file-system
parameters for optimum performance, and at the bottom of a few pages of
wizardly inscriptions was a ‘BUGS’ section consisting of the
line You can tune a file system, but you can't tunafish
.
Variants of this can be seen in other BSD versions, though it has been
excised from some versions by humorless management
droids. The [nt]roff source for SunOS 4.1.1
contains a comment apparently designed to prevent this: Take this
out and a Unix Demon will dog your steps from now until the
time_t
's wrap around.
[It has since been pointed out that indeed you can tunafish. Usually at a canning factory... —ESR]