Re: Code sharing between system and home services (was Re: On the naming of System and Home services modules.)

[Maxime Devos <maximedevos@telenet.be>]

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Ludovic Courtès schreef op za 02-10-2021 om 16:27 [+0200]:
> Maxime Devos <maximedevos@telenet.be> skribis:
> 
> > Ludovic Courtès schreef op di 28-09-2021 om 14:21 [+0200]:
> > > Hi,
> > > 
> > > Joshua Branson <jbranso@dismail.de> skribis:
> > > 
> > > > Apologies if I'm speaking for something I know very little
> > > > about...Wouldn't it be nice if guix home services would accept a user
> > > > and a group field?  For the syncthing service, perhaps the user wants to
> > > > limit Syncthing's runtime permissions.  So instead of running as the
> > > > user, the user would run synthing as a different user with less permissions?
> > > 
> > > That’s not possible unless the calling user is root, since you’d need
> > > the ability to switch users somehow.
> > 
> > On Debian, a user has a list of ‘subordinate user IDs’ which can be switched
> > to without root: <https://manpages.debian.org/buster/uidmap/newuidmap.1.en.html>;.
> > 
> > Maybe "guix home" could use that mechanism, and this mechanism could be implemented
> > on Guix System as well?
> 
> Yes but that requires unprivileged user namespaces, which may or may not
> be supported—e.g., likely unsupported when using Home on a foreign
> distro.

I don't recall newuidmap requiring unprivileged user namespaces -- it's a setuid binary.
It being unsupported on some foreign distros (*) that aren't Debian doesn't seem
a big problem to me, as long as its use is optional and the limitation is documented.

(*) It's upported on Debian, presumably all Debian derivatives, NixOS
(https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/config/users-groups.nix#L179),
on Guix System according to the output of "type newuidmap" though Guix System
doesn't setup /etc/subuid yet.  That covers a lot of GNU/Linux systems, though certainly not all.

Greetings,
Maxime

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