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nixpkgs/nixos/modules/virtualisation/oci-containers.nix
2021-01-29 18:29:07 +01:00

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Nix

{ config, options, lib, pkgs, ... }:
with lib;
let
cfg = config.virtualisation.oci-containers;
proxy_env = config.networking.proxy.envVars;
defaultBackend = options.virtualisation.oci-containers.backend.default;
containerOptions =
{ ... }: {
options = {
image = mkOption {
type = with types; str;
description = "OCI image to run.";
example = "library/hello-world";
};
imageFile = mkOption {
type = with types; nullOr package;
default = null;
description = ''
Path to an image file to load instead of pulling from a registry.
If defined, do not pull from registry.
You still need to set the <literal>image</literal> attribute, as it
will be used as the image name for docker to start a container.
'';
example = literalExample "pkgs.dockerTools.buildDockerImage {...};";
};
cmd = mkOption {
type = with types; listOf str;
default = [];
description = "Commandline arguments to pass to the image's entrypoint.";
example = literalExample ''
["--port=9000"]
'';
};
entrypoint = mkOption {
type = with types; nullOr str;
description = "Override the default entrypoint of the image.";
default = null;
example = "/bin/my-app";
};
environment = mkOption {
type = with types; attrsOf str;
default = {};
description = "Environment variables to set for this container.";
example = literalExample ''
{
DATABASE_HOST = "db.example.com";
DATABASE_PORT = "3306";
}
'';
};
log-driver = mkOption {
type = types.str;
default = "journald";
description = ''
Logging driver for the container. The default of
<literal>"journald"</literal> means that the container's logs will be
handled as part of the systemd unit.
For more details and a full list of logging drivers, refer to respective backends documentation.
For Docker:
<link xlink:href="https://docs.docker.com/engine/reference/run/#logging-drivers---log-driver">Docker engine documentation</link>
For Podman:
Refer to the docker-run(1) man page.
'';
};
ports = mkOption {
type = with types; listOf str;
default = [];
description = ''
Network ports to publish from the container to the outer host.
Valid formats:
<itemizedlist>
<listitem>
<para>
<literal>&lt;ip&gt;:&lt;hostPort&gt;:&lt;containerPort&gt;</literal>
</para>
</listitem>
<listitem>
<para>
<literal>&lt;ip&gt;::&lt;containerPort&gt;</literal>
</para>
</listitem>
<listitem>
<para>
<literal>&lt;hostPort&gt;:&lt;containerPort&gt;</literal>
</para>
</listitem>
<listitem>
<para>
<literal>&lt;containerPort&gt;</literal>
</para>
</listitem>
</itemizedlist>
Both <literal>hostPort</literal> and
<literal>containerPort</literal> can be specified as a range of
ports. When specifying ranges for both, the number of container
ports in the range must match the number of host ports in the
range. Example: <literal>1234-1236:1234-1236/tcp</literal>
When specifying a range for <literal>hostPort</literal> only, the
<literal>containerPort</literal> must <emphasis>not</emphasis> be a
range. In this case, the container port is published somewhere
within the specified <literal>hostPort</literal> range. Example:
<literal>1234-1236:1234/tcp</literal>
Refer to the
<link xlink:href="https://docs.docker.com/engine/reference/run/#expose-incoming-ports">
Docker engine documentation</link> for full details.
'';
example = literalExample ''
[
"8080:9000"
]
'';
};
user = mkOption {
type = with types; nullOr str;
default = null;
description = ''
Override the username or UID (and optionally groupname or GID) used
in the container.
'';
example = "nobody:nogroup";
};
volumes = mkOption {
type = with types; listOf str;
default = [];
description = ''
List of volumes to attach to this container.
Note that this is a list of <literal>"src:dst"</literal> strings to
allow for <literal>src</literal> to refer to
<literal>/nix/store</literal> paths, which would be difficult with an
attribute set. There are also a variety of mount options available
as a third field; please refer to the
<link xlink:href="https://docs.docker.com/engine/reference/run/#volume-shared-filesystems">
docker engine documentation</link> for details.
'';
example = literalExample ''
[
"volume_name:/path/inside/container"
"/path/on/host:/path/inside/container"
]
'';
};
workdir = mkOption {
type = with types; nullOr str;
default = null;
description = "Override the default working directory for the container.";
example = "/var/lib/hello_world";
};
dependsOn = mkOption {
type = with types; listOf str;
default = [];
description = ''
Define which other containers this one depends on. They will be added to both After and Requires for the unit.
Use the same name as the attribute under <literal>virtualisation.oci-containers.containers</literal>.
'';
example = literalExample ''
virtualisation.oci-containers.containers = {
node1 = {};
node2 = {
dependsOn = [ "node1" ];
}
}
'';
};
extraOptions = mkOption {
type = with types; listOf str;
default = [];
description = "Extra options for <command>${defaultBackend} run</command>.";
example = literalExample ''
["--network=host"]
'';
};
autoStart = mkOption {
type = types.bool;
default = true;
description = ''
When enabled, the container is automatically started on boot.
If this option is set to false, the container has to be started on-demand via its service.
'';
};
};
};
mkService = name: container: let
dependsOn = map (x: "${cfg.backend}-${x}.service") container.dependsOn;
in {
wantedBy = [] ++ optional (container.autoStart) "multi-user.target";
after = lib.optionals (cfg.backend == "docker") [ "docker.service" "docker.socket" ] ++ dependsOn;
requires = dependsOn;
environment = proxy_env;
path =
if cfg.backend == "docker" then [ config.virtualisation.docker.package ]
else if cfg.backend == "podman" then [ config.virtualisation.podman.package ]
else throw "Unhandled backend: ${cfg.backend}";
preStart = ''
${cfg.backend} rm -f ${name} || true
${optionalString (container.imageFile != null) ''
${cfg.backend} load -i ${container.imageFile}
''}
'';
script = concatStringsSep " \\\n " ([
"exec ${cfg.backend} run"
"--rm"
"--name=${escapeShellArg name}"
"--log-driver=${container.log-driver}"
] ++ optional (container.entrypoint != null)
"--entrypoint=${escapeShellArg container.entrypoint}"
++ (mapAttrsToList (k: v: "-e ${escapeShellArg k}=${escapeShellArg v}") container.environment)
++ map (p: "-p ${escapeShellArg p}") container.ports
++ optional (container.user != null) "-u ${escapeShellArg container.user}"
++ map (v: "-v ${escapeShellArg v}") container.volumes
++ optional (container.workdir != null) "-w ${escapeShellArg container.workdir}"
++ map escapeShellArg container.extraOptions
++ [container.image]
++ map escapeShellArg container.cmd
);
preStop = "[ $SERVICE_RESULT = success ] || ${cfg.backend} stop ${name}";
postStop = "${cfg.backend} rm -f ${name} || true";
serviceConfig = {
StandardOutput = "null";
StandardError = "null";
### There is no generalized way of supporting `reload` for docker
### containers. Some containers may respond well to SIGHUP sent to their
### init process, but it is not guaranteed; some apps have other reload
### mechanisms, some don't have a reload signal at all, and some docker
### images just have broken signal handling. The best compromise in this
### case is probably to leave ExecReload undefined, so `systemctl reload`
### will at least result in an error instead of potentially undefined
### behaviour.
###
### Advanced users can still override this part of the unit to implement
### a custom reload handler, since the result of all this is a normal
### systemd service from the perspective of the NixOS module system.
###
# ExecReload = ...;
###
TimeoutStartSec = 0;
TimeoutStopSec = 120;
Restart = "always";
};
};
in {
imports = [
(
lib.mkChangedOptionModule
[ "docker-containers" ]
[ "virtualisation" "oci-containers" ]
(oldcfg: {
backend = "docker";
containers = lib.mapAttrs (n: v: builtins.removeAttrs (v // {
extraOptions = v.extraDockerOptions or [];
}) [ "extraDockerOptions" ]) oldcfg.docker-containers;
})
)
];
options.virtualisation.oci-containers = {
backend = mkOption {
type = types.enum [ "podman" "docker" ];
default =
# TODO: Once https://github.com/NixOS/nixpkgs/issues/77925 is resolved default to podman
# if versionAtLeast config.system.stateVersion "20.09" then "podman"
# else "docker";
"docker";
description = "The underlying Docker implementation to use.";
};
containers = mkOption {
default = {};
type = types.attrsOf (types.submodule containerOptions);
description = "OCI (Docker) containers to run as systemd services.";
};
};
config = lib.mkIf (cfg.containers != {}) (lib.mkMerge [
{
systemd.services = mapAttrs' (n: v: nameValuePair "${cfg.backend}-${n}" (mkService n v)) cfg.containers;
}
(lib.mkIf (cfg.backend == "podman") {
virtualisation.podman.enable = true;
})
(lib.mkIf (cfg.backend == "docker") {
virtualisation.docker.enable = true;
})
]);
}