Imperative Container Management¶
We’ll cover imperative container management using
nixos-container first. Be aware that container management
is currently only possible as root.
You create a container with identifier foo as follows:
# nixos-container create foo
This creates the container’s root directory in
/var/lib/containers/foo and a small configuration file
in /etc/containers/foo.conf. It also builds the
container’s initial system configuration and stores it in
/nix/var/nix/profiles/per-container/foo/system. You can
modify the initial configuration of the container on the command line. For
instance, to create a container that has sshd running,
with the given public key for root:
# nixos-container create foo --config '
:ref:`opt-services.openssh.enable` = true;
`users.users.root.openssh.authorizedKeys.keys <None>`_ = \["ssh-dss AAAAB3N…"];
'
By default the next free address in the 10.233.0.0/16 subnet will be chosen
as container IP. This behavior can be altered by setting --host-address and
--local-address:
# nixos-container create test --config-file test-container.nix \\
--local-address 10.235.1.2 --host-address 10.235.1.1
Creating a container does not start it. To start the container, run:
# nixos-container start foo
This command will return as soon as the container has booted and has reached
multi-user.target. On the host, the container runs within
a systemd unit called
container@*container-name*.service.
Thus, if something went wrong, you can get status info using
systemctl:
# systemctl status container@foo
If the container has started successfully, you can log in as root using the root-login operation:
# nixos-container root-login foo
\[root@foo:~]#
Note that only root on the host can do this (since there is no authentication). You can also get a regular login prompt using the login operation, which is available to all users on the host:
# nixos-container login foo
foo login: alice
Password: \***
With nixos-container run, you can execute arbitrary commands in the container:
# nixos-container run foo -- uname -a
Linux foo 3.4.82 #1-NixOS SMP Thu Mar 20 14:44:05 UTC 2014 x86_64 GNU/Linux
There are several ways to change the configuration of the container. First,
on the host, you can edit
/var/lib/container/*name*/etc/nixos/configuration.nix,
and run
# nixos-container update foo
This will build and activate the new configuration. You can also specify a new configuration on the command line:
# nixos-container update foo --config '
:ref:`opt-services.httpd.enable` = true;
:ref:`opt-services.httpd.adminAddr` = "foo@example.org";
:ref:`opt-networking.firewall.allowedTCPPorts` = [ 80 ];
'
# curl http://$(nixos-container show-ip foo)/
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">…
However, note that this will overwrite the container’s
/etc/nixos/configuration.nix.
Alternatively, you can change the configuration from within the container itself by running nixos-rebuild switch inside the container. Note that the container by default does not have a copy of the NixOS channel, so you should run nix-channel --update first.
Containers can be stopped and started using nixos-container
stop and nixos-container start, respectively, or
by using systemctl on the container’s service unit. To
destroy a container, including its file system, do
# nixos-container destroy foo