Hi again,

Marius Bakke <mbakke@fastmail.com> skribis:

> After reconfiguring on the 'core-updates' branch, systems using the
> OpenSSH service will occasionally (not always!) hang forever during
> boot, waiting for entropy.  Moving the mouse or mashing the keyboard
> allows the boot to proceed.
>
> I don't think this is limited to OpenSSH, but anything that calls
> getrandom() during startup.
>
> There is some information about this problem and various workarounds
> here, including links to recent LKML discussions:
>
> https://daniel-lange.com/archives/152-hello-buster.html

I read some of these, and our ‘urandom-seed-service-type’ has the same
bug as <https://github.com/systemd/systemd/issues/4271>.  Namely, we
write the previous seed to /dev/urandom but we don’t credit the
entropy.

The attached patch fixes that, and I think it should fix the problem you
reported.  Could people give it a try?

I’m interested in seeing the value of
/proc/sys/kernel/random/entropy_avail with and without this patch right
after boot (don’t try it in ‘guix system vm’ because there’s no seed
there.)

I wasn’t sure how much to add to the entropy count, but I think it’s
safe to account for all the bits of the seed since we know that it comes
from /dev/urandom.

Thoughts?

Ludo’.