diff --git a/nixos/doc/manual/containers.xml b/nixos/doc/manual/containers.xml new file mode 100644 index 000000000000..b8f170fc614f --- /dev/null +++ b/nixos/doc/manual/containers.xml @@ -0,0 +1,242 @@ + + +Containers + +NixOS allows you to easily run other NixOS instances as +containers. Containers are a light-weight +approach to virtualisation that runs software in the container at the +same speed as in the host system. NixOS containers share the Nix store +of the host, making container creation very efficient. + +Currently, NixOS containers are not perfectly isolated +from the host system. This means that a user with root access to the +container can do things that affect the host. So you should not give +container root access to untrusted users. + +NixOS containers can be created in two ways: imperatively, using +the command nixos-container, and declaratively, by +specifying them in your configuration.nix. The +declarative approach implies that containers get upgraded along with +your host system when you run nixos-rebuild, which +is often not what you want. By contrast, in the imperative approach, +containers are configured and updated independently from the host +system. + + +
Imperative container management + +We’ll cover imperative container management using +nixos-container first. 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 'services.openssh.enable = true; \ + users.extraUsers.root.openssh.authorizedKeys.keys = ["ssh-dss AAAAB3N…"];' + + + + +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 succesfully, 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 'services.httpd.enable = true; \ + services.httpd.adminAddr = "foo@example.org";' + +$ 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 + + + + +
+ + +
Declarative container specification + +You can also specify containers and their configuration in the +host’s configuration.nix. For example, the +following specifies that there shall be a container named +database running PostgreSQL: + + +containers.database = + { config = + { config, pkgs, ... }: + { services.postgresql.enable = true; + services.postgresql.package = pkgs.postgresql92; + }; + }; + + +If you run nixos-rebuild switch, the container will +be built and started. If the container was already running, it will be +updated in place, without rebooting. + +By default, declarative containers share the network namespace +of the host, meaning that they can listen on (privileged) +ports. However, they cannot change the network configuration. You can +give a container its own network as follows: + + +containers.database = + { privateNetwork = true; + hostAddress = "192.168.100.10"; + localAddress = "192.168.100.11"; + }; + + +This gives the container a private virtual Ethernet interface with IP +address 192.168.100.11, which is hooked up to a +virtual Ethernet interface on the host with IP address +192.168.100.10. (See the next section for details +on container networking.) + +To disable the container, just remove it from +configuration.nix and run nixos-rebuild +switch. Note that this will not delete the root directory of +the container in /var/lib/containers. + +
+ + +
Networking + +When you create a container using nixos-container +create, it gets it own private IPv4 address in the range +10.233.0.0/16. You can get the container’s IPv4 +address as follows: + + +$ nixos-container show-ip foo +10.233.4.2 + +$ ping -c1 10.233.4.2 +64 bytes from 10.233.4.2: icmp_seq=1 ttl=64 time=0.106 ms + + + + +Networking is implemented using a pair of virtual Ethernet +devices. The network interface in the container is called +eth0, while the matching interface in the host is +called c-container-name +(e.g., c-foo). The container has its own network +namespace and the CAP_NET_ADMIN capability, so it +can perform arbitrary network configuration such as setting up +firewall rules, without affecting or having access to the host’s +network. + +By default, containers cannot talk to the outside network. If +you want that, you should set up Network Address Translation (NAT) +rules on the host to rewrite container traffic to use your external +IP address. This can be accomplished using the following configuration +on the host: + + +networking.nat.enable = true; +networking.nat.internalInterfaces = ["c-+"]; +networking.nat.externalInterface = "eth0"; + +where eth0 should be replaced with the desired +external interface. Note that c-+ is a wildcard +that matches all container interfaces. + +
+ + + + diff --git a/nixos/doc/manual/manual.xml b/nixos/doc/manual/manual.xml index f9775f4f0170..5753a8ff9e74 100644 --- a/nixos/doc/manual/manual.xml +++ b/nixos/doc/manual/manual.xml @@ -54,6 +54,7 @@ + diff --git a/nixos/modules/virtualisation/containers.nix b/nixos/modules/virtualisation/containers.nix index fbdd3f9034c6..c53bd7d3509d 100644 --- a/nixos/modules/virtualisation/containers.nix +++ b/nixos/modules/virtualisation/containers.nix @@ -281,6 +281,8 @@ in ''; }) config.containers; + # FIXME: auto-start containers. + # Generate /etc/hosts entries for the containers. networking.extraHosts = concatStrings (mapAttrsToList (name: cfg: optionalString (cfg.localAddress != null) ''