Re: boot time on Linux

[Po Lu]

Paul Eggert <eggert@cs.ucla.edu> writes:

> [For those cc'ed, the thread's at <https://bugs.gnu.org/64937#142>.]
>
> On 2023-08-09 07:29, Bruno Haible wrote:
>
>> And on Alpine Linux, while /var/run/utmp is empty, its time stamp is
>> essentially the boot time.
>> The approach used by Emacs, namely to look at the time stamp of
>> /var/run/random-seed, is therefore essentially one of the best
>> approaches.
>> It just needs to also look at /var/lib/systemd/random-seed and - on
>> Alpine
>> Linux - /var/run/utmp .
>
> Thanks for looking into this. Clearly Emacs had some catching up to
> do, since it was using a location for the random-seed file that
> current GNU/Linux distros no longer use. To try to fix this I
> installed the attached patch to Emacs master on Savannah.
>
> This patch does not address the problem for Alpine, nor I suspect for
> Android. I suppose Alpine could use the timestamp of /var/run/utmp (or
> is that /run/utmp?) but I don't know how 'configure' would reliably
> detect it's being built or cross-built for Alpine. I'll cc this to
> Natanael Copa, who does the Alpine ports for Emacs, to see whether he
> can give advice.
>
> Also, I don't know how Android records boot time so I'll cc this to Po
> Lu, the main developer for Emacs on Android.

The boot time is off limits to user programs on Android, for security
reasons.  It should suffice to undefine BOOT_TIME_FILE there.