docker-rootless service: init

nixos/doc/manual/from_md/release-notes/rl-2205.section.xml

···
       </listitem>
       <listitem>
         <para>
+          <link xlink:href="https://docs.docker.com/engine/security/rootless/">rootless
+          Docker</link>, a <literal>systemd --user</literal> Docker
+          service which runs without root permissions. Available as
+          <link xlink:href="options.html#opt-virtualisation.docker.rootless.enable">virtualisation.docker.rootless.enable</link>.
+        </para>
+      </listitem>
+      <listitem>
+        <para>
           <link xlink:href="https://www.elastic.co/guide/en/beats/filebeat/current/filebeat-overview.html">filebeat</link>,
           a lightweight shipper for forwarding and centralizing log
           data. Available as

nixos/doc/manual/release-notes/rl-2205.section.md

···
 ## New Services {#sec-release-22.05-new-services}
 
 - [aesmd](https://github.com/intel/linux-sgx#install-the-intelr-sgx-psw), the Intel SGX Architectural Enclave Service Manager. Available as [services.aesmd](#opt-services.aesmd.enable).
+- [rootless Docker](https://docs.docker.com/engine/security/rootless/), a `systemd --user` Docker service which runs without root permissions. Available as [virtualisation.docker.rootless.enable](options.html#opt-virtualisation.docker.rootless.enable).
 
 - [filebeat](https://www.elastic.co/guide/en/beats/filebeat/current/filebeat-overview.html), a lightweight shipper for forwarding and centralizing log data. Available as [services.filebeat](#opt-services.filebeat.enable).
 

nixos/modules/module-list.nix

···
   ./virtualisation/oci-containers.nix
   ./virtualisation/cri-o.nix
   ./virtualisation/docker.nix
+  ./virtualisation/docker-rootless.nix
   ./virtualisation/ecs-agent.nix
   ./virtualisation/libvirtd.nix
   ./virtualisation/lxc.nix

nixos/modules/virtualisation/docker-rootless.nix

···
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+
+  cfg = config.virtualisation.docker.rootless;
+  proxy_env = config.networking.proxy.envVars;
+  settingsFormat = pkgs.formats.json {};
+  daemonSettingsFile = settingsFormat.generate "daemon.json" cfg.daemon.settings;
+
+in
+
+{
+  ###### interface
+
+  options.virtualisation.docker.rootless = {
+    enable = mkOption {
+      type = types.bool;
+      default = false;
+      description = ''
+        This option enables docker in a rootless mode, a daemon that manages
+        linux containers. To interact with the daemon, one needs to set
+        <command>DOCKER_HOST=unix://$XDG_RUNTIME_DIR/docker.sock</command>.
+      '';
+    };
+
+    setSocketVariable = mkOption {
+      type = types.bool;
+      default = false;
+      description = ''
+        Point <command>DOCKER_HOST</command> to rootless Docker instance for
+        normal users by default.
+      '';
+    };
+
+    daemon.settings = mkOption {
+      type = settingsFormat.type;
+      default = { };
+      example = {
+        ipv6 = true;
+        "fixed-cidr-v6" = "fd00::/80";
+      };
+      description = ''
+        Configuration for docker daemon. The attributes are serialized to JSON used as daemon.conf.
+        See https://docs.docker.com/engine/reference/commandline/dockerd/#daemon-configuration-file
+      '';
+    };
+
+    package = mkOption {
+      default = pkgs.docker;
+      defaultText = literalExpression "pkgs.docker";
+      type = types.package;
+      example = literalExpression "pkgs.docker-edge";
+      description = ''
+        Docker package to be used in the module.
+      '';
+    };
+  };
+
+  ###### implementation
+
+  config = mkIf cfg.enable {
+    environment.systemPackages = [ cfg.package ];
+
+    environment.extraInit = optionalString cfg.setSocketVariable ''
+      if [ -z "$DOCKER_HOST" -a -n "$XDG_RUNTIME_DIR" ]; then
+        export DOCKER_HOST="unix://$XDG_RUNTIME_DIR/docker.sock"
+      fi
+    '';
+
+    # Taken from https://github.com/moby/moby/blob/master/contrib/dockerd-rootless-setuptool.sh
+    systemd.user.services.docker = {
+      wantedBy = [ "default.target" ];
+      description = "Docker Application Container Engine (Rootless)";
+      # needs newuidmap from pkgs.shadow
+      path = [ "/run/wrappers" ];
+      environment = proxy_env;
+      unitConfig.StartLimitInterval = "60s";
+      serviceConfig = {
+        Type = "notify";
+        ExecStart = "${cfg.package}/bin/dockerd-rootless --config-file=${daemonSettingsFile}";
+        ExecReload = "${pkgs.procps}/bin/kill -s HUP $MAINPID";
+        TimeoutSec = 0;
+        RestartSec = 2;
+        Restart = "always";
+        StartLimitBurst = 3;
+        LimitNOFILE = "infinity";
+        LimitNPROC = "infinity";
+        LimitCORE = "infinity";
+        Delegate = true;
+        NotifyAccess = "all";
+        KillMode = "mixed";
+      };
+    };
+  };
+
+}

nixos/tests/all-tests.nix

···
   dnscrypt-wrapper = handleTestOn ["x86_64-linux"] ./dnscrypt-wrapper {};
   doas = handleTest ./doas.nix {};
   docker = handleTestOn ["x86_64-linux"] ./docker.nix {};
+  docker-rootless = handleTestOn ["x86_64-linux"] ./docker-rootless.nix {};
   docker-edge = handleTestOn ["x86_64-linux"] ./docker-edge.nix {};
   docker-registry = handleTest ./docker-registry.nix {};
   docker-tools = handleTestOn ["x86_64-linux"] ./docker-tools.nix {};

nixos/tests/docker-rootless.nix

···
+# This test runs docker and checks if simple container starts
+
+import ./make-test-python.nix ({ lib, pkgs, ...} : {
+  name = "docker-rootless";
+  meta = with pkgs.lib.maintainers; {
+    maintainers = [ abbradar ];
+  };
+
+  nodes = {
+    machine = { pkgs, ... }: {
+      virtualisation.docker.rootless.enable = true;
+
+      users.users.alice = {
+        uid = 1000;
+        isNormalUser = true;
+      };
+    };
+  };
+
+  testScript = { nodes, ... }:
+    let
+      user = nodes.machine.config.users.users.alice;
+      sudo = lib.concatStringsSep " " [
+        "XDG_RUNTIME_DIR=/run/user/${toString user.uid}"
+        "DOCKER_HOST=unix:///run/user/${toString user.uid}/docker.sock"
+        "sudo" "--preserve-env=XDG_RUNTIME_DIR,DOCKER_HOST" "-u" "alice"
+      ];
+    in ''
+      machine.wait_for_unit("multi-user.target")
+
+      machine.succeed("loginctl enable-linger alice")
+      machine.wait_until_succeeds("${sudo} systemctl --user is-active docker.service")
+
+      machine.succeed("tar cv --files-from /dev/null | ${sudo} docker import - scratchimg")
+      machine.succeed(
+          "${sudo} docker run -d --name=sleeping -v /nix/store:/nix/store -v /run/current-system/sw/bin:/bin scratchimg /bin/sleep 10"
+      )
+      machine.succeed("${sudo} docker ps | grep sleeping")
+      machine.succeed("${sudo} docker stop sleeping")
+    '';
+})