Postgres was taking a long time to shutdown. This is because we were
sending SIGINT to all processes, apparently confusing the autovacuum
launcher. Instead it should only be sent to the main process (which
takes care of shutting down the others).
The downside is that systemd will also send the final SIGKILL only to
the main process, so other processes in the cgroup may be left behind.
There should be an option for this...
You can now say:
systemd.containers.foo.config =
{ services.openssh.enable = true;
services.openssh.ports = [ 2022 ];
users.extraUsers.root.openssh.authorizedKeys.keys = [ "ssh-dss ..." ];
};
which defines a NixOS instance with the given configuration running
inside a lightweight container.
You can also manage the configuration of the container independently
from the host:
systemd.containers.foo.path = "/nix/var/nix/profiles/containers/foo";
where "path" is a NixOS system profile. It can be created/updated by
doing:
$ nix-env --set -p /nix/var/nix/profiles/containers/foo \
-f '<nixos>' -A system -I nixos-config=foo.nix
The container configuration (foo.nix) should define
boot.isContainer = true;
to optimise away the building of a kernel and initrd. This is done
automatically when using the "config" route.
On the host, a lightweight container appears as the service
"container-<name>.service". The container is like a regular NixOS
(virtual) machine, except that it doesn't have its own kernel. It has
its own root file system (by default /var/lib/containers/<name>), but
shares the Nix store of the host (as a read-only bind mount). It also
has access to the network devices of the host.
Currently, if the configuration of the container changes, running
"nixos-rebuild switch" on the host will cause the container to be
rebooted. In the future we may want to send some message to the
container so that it can activate the new container configuration
without rebooting.
Containers are not perfectly isolated yet. In particular, the host's
/sys/fs/cgroup is mounted (writable!) in the guest.
The attribute ‘config.systemd.services.<service-name>.runner’
generates a script that runs the service outside of systemd. This is
useful for testing, and also allows NixOS services to be used outside
of NixOS. For instance, given a configuration file foo.nix:
{ config, pkgs, ... }:
{ services.postgresql.enable = true;
services.postgresql.package = pkgs.postgresql92;
services.postgresql.dataDir = "/tmp/postgres";
}
you can build and run PostgreSQL as follows:
$ nix-build -A config.systemd.services.postgresql.runner -I nixos-config=./foo.nix
$ ./result
This will run the service's ExecStartPre, ExecStart, ExecStartPost and
ExecStopPost commands in an appropriate environment. It doesn't work
well yet for "forking" services, since it can't track the main
process. It also doesn't work for services that assume they're always
executed by root.
(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"
- It now uses JavaScript for configuration (only),
so I had to "convert" config for NetworkManager.
- I tested suspend/restart/(un)mount on KDE/Xfce,
Phreedom tested NetworkManager config conversion.
Gnome doesn't work at least since I started using NixOS half a year
ago, let's not give wrong impressions to newcomers. Packaging gnome3
is still something on horizon.
