NixOS: Run Docker containers as declarative systemd services (#55179)

* WIP: Run Docker containers as declarative systemd services

* PR feedback round 1

* docker-containers: add environment, ports, user, workdir options

* docker-containers: log-driver, string->str, line wrapping

* ExecStart instead of script wrapper, %n for container name

* PR feedback: better description and example formatting

* Fix docbook formatting (oops)

* Use a list of strings for ports, expand documentation

* docker-continers: add a simple nixos test

* waitUntilSucceeds to avoid potential weird async issues

* Don't enable docker daemon unless we actually need it

* PR feedback: leave ExecReload undefined

1 files changed, 29 insertions, 0 deletions

diff --git a/nixos/tests/docker-containers.nix b/nixos/tests/docker-containers.nix
new file mode 100644
index 000000000000..972552735202
--- /dev/null
+++ b/nixos/tests/docker-containers.nix
@@ -0,0 +1,29 @@
+# Test Docker containers as systemd units
+
+import ./make-test.nix ({ pkgs, lib, ... }: {
+  name = "docker-containers";
+  meta = {
+    maintainers = with lib.maintainers; [ benley ];
+  };
+
+  nodes = {
+    docker = { pkgs, ... }:
+      {
+        virtualisation.docker.enable = true;
+
+        virtualisation.dockerPreloader.images = [ pkgs.dockerTools.examples.nginx ];
+
+        docker-containers.nginx = {
+          image = "nginx-container";
+          ports = ["8181:80"];
+        };
+      };
+  };
+
+  testScript = ''
+    startAll;
+    $docker->waitForUnit("docker-nginx.service");
+    $docker->waitForOpenPort(8181);
+    $docker->waitUntilSucceeds("curl http://localhost:8181|grep Hello");
+  '';
+})