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123 lines
5.1 KiB
123 lines
5.1 KiB
<section xmlns="http://docbook.org/ns/docbook"
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xmlns:xlink="http://www.w3.org/1999/xlink"
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xmlns:xi="http://www.w3.org/2001/XInclude"
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version="5.0"
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xml:id="sec-imperative-containers">
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<title>Imperative Container Management</title>
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<para>
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We’ll cover imperative container management using
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<command>nixos-container</command> first. Be aware that container management
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is currently only possible as <literal>root</literal>.
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</para>
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<para>
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You create a container with identifier <literal>foo</literal> as follows:
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<screen>
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<prompt># </prompt>nixos-container create <replaceable>foo</replaceable>
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</screen>
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This creates the container’s root directory in
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<filename>/var/lib/containers/<replaceable>foo</replaceable></filename> and a small configuration file
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in <filename>/etc/containers/<replaceable>foo</replaceable>.conf</filename>. It also builds the
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container’s initial system configuration and stores it in
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<filename>/nix/var/nix/profiles/per-container/<replaceable>foo</replaceable>/system</filename>. You can
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modify the initial configuration of the container on the command line. For
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instance, to create a container that has <command>sshd</command> running,
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with the given public key for <literal>root</literal>:
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<screen>
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<prompt># </prompt>nixos-container create <replaceable>foo</replaceable> --config '
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<xref linkend="opt-services.openssh.enable"/> = true;
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<link linkend="opt-users.users._name_.openssh.authorizedKeys.keys">users.users.root.openssh.authorizedKeys.keys</link> = ["ssh-dss AAAAB3N…"];
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'
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</screen>
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By default the next free address in the <literal>10.233.0.0/16</literal> subnet will be chosen
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as container IP. This behavior can be altered by setting <literal>--host-address</literal> and
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<literal>--local-address</literal>:
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<screen>
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<prompt># </prompt>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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</screen>
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</para>
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<para>
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Creating a container does not start it. To start the container, run:
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<screen>
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<prompt># </prompt>nixos-container start <replaceable>foo</replaceable>
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</screen>
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This command will return as soon as the container has booted and has reached
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<literal>multi-user.target</literal>. On the host, the container runs within
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a systemd unit called
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<literal>container@<replaceable>container-name</replaceable>.service</literal>.
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Thus, if something went wrong, you can get status info using
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<command>systemctl</command>:
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<screen>
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<prompt># </prompt>systemctl status container@<replaceable>foo</replaceable>
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</screen>
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</para>
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<para>
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If the container has started successfully, you can log in as root using the
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<command>root-login</command> operation:
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<screen>
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<prompt># </prompt>nixos-container root-login <replaceable>foo</replaceable>
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<prompt>[root@foo:~]#</prompt>
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</screen>
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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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<command>login</command> operation, which is available to all users on the
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host:
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<screen>
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<prompt># </prompt>nixos-container login <replaceable>foo</replaceable>
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foo login: alice
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Password: ***
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</screen>
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With <command>nixos-container run</command>, you can execute arbitrary
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commands in the container:
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<screen>
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<prompt># </prompt>nixos-container run <replaceable>foo</replaceable> -- 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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</screen>
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</para>
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<para>
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There are several ways to change the configuration of the container. First,
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on the host, you can edit
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<literal>/var/lib/container/<replaceable>name</replaceable>/etc/nixos/configuration.nix</literal>,
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and run
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<screen>
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<prompt># </prompt>nixos-container update <replaceable>foo</replaceable>
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</screen>
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This will build and activate the new configuration. You can also specify a
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new configuration on the command line:
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<screen>
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<prompt># </prompt>nixos-container update <replaceable>foo</replaceable> --config '
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<xref linkend="opt-services.httpd.enable"/> = true;
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<xref linkend="opt-services.httpd.adminAddr"/> = "foo@example.org";
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<xref linkend="opt-networking.firewall.allowedTCPPorts"/> = [ 80 ];
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'
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<prompt># </prompt>curl http://$(nixos-container show-ip <replaceable>foo</replaceable>)/
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">…
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</screen>
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However, note that this will overwrite the container’s
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<filename>/etc/nixos/configuration.nix</filename>.
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</para>
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<para>
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Alternatively, you can change the configuration from within the container
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itself by running <command>nixos-rebuild switch</command> inside the
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container. Note that the container by default does not have a copy of the
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NixOS channel, so you should run <command>nix-channel --update</command>
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first.
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</para>
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<para>
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Containers can be stopped and started using <literal>nixos-container
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stop</literal> and <literal>nixos-container start</literal>, respectively, or
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by using <command>systemctl</command> on the container’s service unit. To
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destroy a container, including its file system, do
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<screen>
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<prompt># </prompt>nixos-container destroy <replaceable>foo</replaceable>
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</screen>
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</para>
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</section>
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