2021-07-02 04:57:33 +01:00
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# Imperative Container Management {#sec-imperative-containers}
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We'll cover imperative container management using `nixos-container`
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first. Be aware that container management is currently only possible as
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`root`.
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You create a container with identifier `foo` as follows:
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```ShellSession
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# nixos-container create foo
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```
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2020-05-08 15:05:29 +01:00
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This creates the container's root directory in `/var/lib/nixos-containers/foo`
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and a small configuration file in `/etc/nixos-containers/foo.conf`. It also
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2021-07-02 04:57:33 +01:00
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builds the container's initial system configuration and stores it in
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`/nix/var/nix/profiles/per-container/foo/system`. You can modify the
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initial configuration of the container on the command line. For
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instance, to create a container that has `sshd` running, with the given
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public key for `root`:
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```ShellSession
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# nixos-container create foo --config '
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services.openssh.enable = true;
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users.users.root.openssh.authorizedKeys.keys = ["ssh-dss AAAAB3N…"];
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'
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```
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By default the next free address in the `10.233.0.0/16` subnet will be
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chosen as container IP. This behavior can be altered by setting
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`--host-address` and `--local-address`:
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```ShellSession
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# nixos-container create test --config-file test-container.nix \
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--local-address 10.235.1.2 --host-address 10.235.1.1
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```
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Creating a container does not start it. To start the container, run:
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```ShellSession
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# nixos-container start foo
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```
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This command will return as soon as the container has booted and has
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reached `multi-user.target`. On the host, the container runs within a
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systemd unit called `container@container-name.service`. Thus, if
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something went wrong, you can get status info using `systemctl`:
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```ShellSession
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# systemctl status container@foo
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```
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If the container has started successfully, you can log in as root using
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the `root-login` operation:
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```ShellSession
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# nixos-container root-login foo
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[root@foo:~]#
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```
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Note that only root on the host can do this (since there is no
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authentication). You can also get a regular login prompt using the
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`login` operation, which is available to all users on the host:
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```ShellSession
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# nixos-container login foo
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foo login: alice
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Password: ***
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```
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With `nixos-container run`, you can execute arbitrary commands in the
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container:
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```ShellSession
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# nixos-container run foo -- uname -a
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Linux foo 3.4.82 #1-NixOS SMP Thu Mar 20 14:44:05 UTC 2014 x86_64 GNU/Linux
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```
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There are several ways to change the configuration of the container.
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First, on the host, you can edit
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`/var/lib/container/name/etc/nixos/configuration.nix`, and run
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```ShellSession
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# nixos-container update foo
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```
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This will build and activate the new configuration. You can also specify
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a new configuration on the command line:
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```ShellSession
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# nixos-container update foo --config '
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services.httpd.enable = true;
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services.httpd.adminAddr = "foo@example.org";
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networking.firewall.allowedTCPPorts = [ 80 ];
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'
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# curl http://$(nixos-container show-ip foo)/
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">…
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```
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However, note that this will overwrite the container's
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`/etc/nixos/configuration.nix`.
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Alternatively, you can change the configuration from within the
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container itself by running `nixos-rebuild switch` inside the container.
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Note that the container by default does not have a copy of the NixOS
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channel, so you should run `nix-channel --update` first.
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Containers can be stopped and started using `nixos-container
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stop` and `nixos-container start`, respectively, or by using
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`systemctl` on the container's service unit. To destroy a container,
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including its file system, do
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```ShellSession
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# nixos-container destroy foo
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```
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