.. _sec-imperative-containers: Imperative Container Management ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ We’ll cover imperative container management using :command:`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 :file:`/var/lib/containers/foo` and a small configuration file in :file:`/etc/containers/foo.conf`. It also builds the container’s initial system configuration and stores it in :file:`/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 :command:`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 `_ = \["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 :command:`systemctl`: :: # systemctl status container@foo If the container has started successfully, you can log in as root using the :command:`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 :command:`login` operation, which is available to all users on the host: :: # nixos-container login foo foo login: alice Password: \*** With :command:`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)/ … However, note that this will overwrite the container’s :file:`/etc/nixos/configuration.nix`. Alternatively, you can change the configuration from within the container itself by running :command:`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 :command:`nix-channel --update` first. Containers can be stopped and started using ``nixos-container stop`` and ``nixos-container start``, respectively, or by using :command:`systemctl` on the container’s service unit. To destroy a container, including its file system, do :: # nixos-container destroy foo