This is mainly useful for specifying mounts that depend on other
units. For example sshfs or davfs need network (and possibly
nameservices).
While systemd makes a distinction between local and remote
filesystems, this only works for in-kernel filesystems such as
nfs and cifs.
fuse-based filesystems (such as sshfs and davs) are classified as
local, so they fail without networking. By explicitly declaring these
mounts as full systemd units (as opposed to having systemd generate
them automatically from /etc/fstab), dependencies can be specified as
on every other unit.
In the future, we can probably port NixOS' filesystems handling to use
these native systemd.mount units and skip /etc/fstab altogether, but
this probably requires additional changes, such as starting systemd
even earlier during boot (stage 1).
Running agetty on ttyS0 interferes with the backdoor, which uses ttyS0
as its standard error. After agetty starts, writes to the stderr file
descriptor will return EIO (though doing "exec 2>/proc/self/fd/2" will
miracuously fix this).
http://hydra.nixos.org/build/3252782
The triggers are just arbitrary strings that are included in the unit
under X-Restart-Triggers. The idea is that if they change between
reconfigurations, switch-to-configuration will restart the unit
because its store path changed. This is mostly useful for services
that implicitly depend on generated files in /etc. Thus you can say
restartTriggers = [ confFile ];
where ‘confFile’ is the derivation that generated the /etc file in
question.
So instead of:
boot.systemd.services."foo".serviceConfig =
''
StartLimitInterval=10
CPUShare=500
'';
you can say:
boot.systemd.services."foo".serviceConfig.StartLimitInterval = 10;
boot.systemd.services."foo".serviceConfig.CPUShare = 500;
This way all unit options are available and users can set/override
options in configuration.nix.
