All activation scripts run in serial upon boot and nixos-rebuild switch
etc., in contrast to preStart which run before a service starts, and can
run in parallel with other services.
The munin(-node) activation script is particularly slow. Change it to a
preStart script so that it can run in parallel with other services and
not slow down boot (or nixos-rebuild switch).
This reduces (repeated) "nixos-rebuild test" time from ~16 seconds to ~8
on my (old) laptop.
Using pkgs.lib on the spine of module evaluation is problematic
because the pkgs argument depends on the result of module
evaluation. To prevent an infinite recursion, pkgs and some of the
modules are evaluated twice, which is inefficient. Using ‘with lib’
prevents this problem.
To be compatible with eb2f44c18c (Generate
/etc/passwd and /etc/group at build time). Without this you'll get this:
$ nixos-rebuild build
[...]
user-thrown exception: The option `users.extraGroups.unnamed-9.1.gid' is used but not defined.
(systemd service descriptions that is, not service descriptions in "man
configuration.nix".)
Capitalizing each word in the description seems to be the accepted
standard.
Also shorten these descriptions:
* "Munin node, the agent process" => "Munin Node"
* "Planet Venus, an awesome ‘river of news’ feed reader" => "Planet Venus Feed Reader"
