Re: A corner case of broken reproducibility

[Maxime Devos]

Ludovic Courtès schreef op wo 01-06-2022 om 18:38 [+0200]:
> There’s a talk by Lennart Poettering where he explains that, contrary to
> what one might think, “chown -R $HOME” turns out to be fast enough that
> systemd-homed can do that unconditionally (off the of my head).

Interesting.
Taking "find $HOME > /dev/null" as an approximation of how long "chown
-R $HOME" would take:

$ time find . > /dev/null 

real    0m7,066s
user    0m0,427s
sys     0m1,341s

Assuming that ‘unconditionally = only chown -R $HOME if the uid of
$HOME isn't what was expected’ (otherwise, +7sec for every boot),
that's not too bad.

That's on a SSD and not a hard disk though, I'd image it would be worse
on a hard disk.

Depending on the size of $HOME, it could be a lot longer though:

$ time find /gnu/store > /dev/null 

real    1m9,729s
user    0m4,135s
sys     0m13,840s

Might still be acceptable as long as uids aren't switched too often ...

Can we, as-is in Guix, assume we can modify /home/foo though?  E.g.
what if it's put on a separate storage medium not attached at boot.

Greetings,
Maxime.

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