Re: [Nicolas Graves] [PATCH v6 01/10] rde: emacs: Start emacs in --daemon mode, with shepherd and pid-file

[Nicolas Graves]

On 2024-04-12 22:38, Ludovic Courtès wrote:

> Hi Nicolas,
>
> Nicolas Graves skribis:
>
>> As promised to Stefan a few months ago, here's a use case of
>> Shepherd/Emacs implementation that we developped in RDE.
>
> Would be nice to have it in Guix Home!

I am commited to merge RDE contributions upstream when this is possible,
I will when it's mature enough / adapted for Guix ;)

>
>> We're using the --daemon option on the Shepherd side to launch the
>> server in the background, include code in Emacs configuration to make it
>> create a pid-file as soon as the server has started, and redefine
>> kill-emacs to be managed by the Shepherd.
>
> Emacs supports systemd-style socket activation so, instead of using a
> PID file, you could use ‘make-systemd-constructor’.
>
> Now, that code in emacs.c is unfortunately implemented via libsystemd
> and thus disabled in Guix.  Using libsystemd in this case is unnecessary
> (and increases the attack surface, as we’ve seen with the xz backdoor):
> it could read the ‘LISTEN_FDS’ and ‘LISTEN_PID’ environment variables
> instead of calling the sd_* functions.
>
>   https://www.freedesktop.org/software/systemd/man/latest/sd_listen_fds.html
>   
> https://www.gnu.org/software/shepherd/manual/html_node/Service-De_002d-and-Constructors.html#index-make_002dsystemd_002dconstructor

Thanks Ludo, that is precisely the feedback I was looking for.

Maybe some feedback on the Emacs side about this? There are indeed very
few places where systemd sd_* functions are called in emacs.c, should we
try and re-implement them instead of using the library as is? Would that
be a contribution Emacs devs would be interested in? That would
definitely be beneficial for Emacs on Guix as highlighted by Ludo'.

>
> Thanks,
> Ludo’.

-- 
Best regards,
Nicolas Graves