[bug#28128] [PATCH 2/2] scripts: system: Support container network sharing.

[Ludovic Courtès]

Hi,

Arun Isaac <address@hidden> skribis:

>>   2. The notion of “shared network” is very much a container (or VM)
>>      thing, so somehow it still doesn’t feel right to me that (gnu
>>      system) has to be aware of these special cases.
>>
>> I think the ‘host-database-service-type’ wouldn’t have this problem, but
>> maybe it has other issues.  I guess this needs more experimentation,
>> sorry for not coming up with clearer ideas!
>
> If these services (the shared-network service, the hosts-database
> service or indeed any other service) had access to the operating-system
> object `os', then they would be able to operate independently without
> having to be extended by `essential-services'. Is this possible somehow?
> Is it a good idea to give services access to the os fields?

It’s not easily possible, and I think it would be a bad idea: if every
service has access to every ‘operating-system’ field, that gives you
more flexibility, but it’s also much harder to reason about what
happens, compared to the current extension graph (the NixOS “module”
system works like that: every service can access every bit of the whole
configuration, but IMO that makes it quite hard to understand.)

What could be useful is “self-referential” records, where a field can
refer to the record it belongs do.  So we’d do:

  (define-record-type* <operating-system>
    ;; …
    (services operating-system-services
              (self-referential? #t) (default essential-services)))

whereby ‘essential-services’ would be passed the <operating-system>
record somehow.

That needs more thought…

Thanks,
Ludo’.