# Imperative Container Management {#sec-imperative-containers} 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: ```ShellSession # 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`: ```ShellSession # nixos-container create foo --config ' 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`: ```ShellSession # 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: ```ShellSession # 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`: ```ShellSession # systemctl status container@foo ``` If the container has started successfully, you can log in as root using the `root-login` operation: ```ShellSession # 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: ```ShellSession # nixos-container login foo foo login: alice Password: *** ``` With `nixos-container run`, you can execute arbitrary commands in the container: ```ShellSession # 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 ```ShellSession # nixos-container update foo ``` This will build and activate the new configuration. You can also specify a new configuration on the command line: ```ShellSession # nixos-container update foo --config ' services.httpd.enable = true; services.httpd.adminAddr = "foo@example.org"; networking.firewall.allowedTCPPorts = [ 80 ]; ' # curl http://$(nixos-container show-ip foo)/ … ``` 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 ```ShellSession # nixos-container destroy foo ```