[Nix-dev] How to get rid of systemd

[Ludovic Courtès]

Ertugrul Söylemez <ertesx at gmx.de> skribis:

> I would prefer and do propose an algebraic solution (view services as a
> toolbox from which you can pick the services you want and compose them
> together).  A services configuration then might look like this:
>
>     services =
>         bitlbee { port = 10000; stateDir = "/var/lib/bitlbee1"; } <>
>         bitlbee { port = 10001; stateDir = "/var/lib/bitlbee2"; } <>
>         nginx { httpConfig = "..."; } <>
>         postfix { postMasterAlias = "blah"; }
>
> The big difference is that now services are first class values and form
> a monoid under composition, which brings a number of advantages:

FWIW, Guix uses an approach along these lines: the ‘bitlbee-service’
function, for instance, returns a ‘service’ object as a monadic value
(see <http://www.gnu.org/software/guix/manual/guix.html#Defining-Services>
for details.)

Unlike in NixOS, the service implementation doesn’t have access to the
rest of the system configuration, which I think is a good thing, as you
note.

What’s unsatisfying (and thus subject to change) is that
‘operating-system’ objects (which are pure declarations) end up with
monadic values in their ‘services’ field.  That makes it inconvenient
to, say, filter items from that list, or to tweak their configuration,
because one first needs to bind them.  That said, it’s probably not a
problem for Nix, because every Nix function is really a function in what
we call the “store monad”.

In your example, what would ‘bitlbee’, ‘nginx’ etc. return exactly?  An
attribute set describing the service?

Anyway, I’m interested in following this discussion.

Thanks,
Ludo’.