[systemd-devel] should random seeds go into /var/cache?

[Jason A. Donenfeld]

Hey,

I've been working on my small seedrng utility, which is more or less
the same thing as systemd-random-seed.service, with a few unimportant
design differences here and there. As I'd worked with
systemd-random-seed.service quite a bit before, its choices comprised
much of my mental model starting out.

One of the things I did like systemd-random-seed.service without
really thinking too much about it is I made use of /var/lib/seedrng/,
just as systemd uses /var/lib/systemd/random-seed/. Seems reasonable
enough I guess. But I was thinking: wouldn't /var/cache/{blah}/ be the
better for this? Seeds are supposed to be somewhat volatile, and
shouldn't be copied between images, and the default behavior of
/var/lib is usually to be copied, whereas /var/cache usually isn't.
There's also /var/tmp too, right? Which is supposed to be never a
tmpfs or something? But "cache" seems a bit more fitting than
"temporary".

Anyway, I'm not really sure what makes the most sense, and it seems
like FHS placement is more of an art than a science. I don't think I'm
super far off, though, in at least wondering whether random seeds
belong in /var/cache rather than /var/lib.

Does anybody have opinions on this? Should I just submit a PR moving
the systemd seeds to /var/cache and see what happens?

Jason