nixpkgs/nixos/tests/containers-tmpfs.nix

import ./make-test-python.nix ({ pkgs, lib, ... }: {
  name = "containers-tmpfs";
  meta = {
    maintainers = with lib.maintainers; [ patryk27 ];
  };

  nodes.machine =
    { pkgs, ... }:
    { imports = [ ../modules/installer/cd-dvd/channel.nix ];
      virtualisation.writableStore = true;

      containers.tmpfs =
        {
          autoStart = true;
          tmpfs = [
            # Mount var as a tmpfs
            "/var"

            # Add a nested mount inside a tmpfs
            "/var/log"

            # Add a tmpfs on a path that does not exist
            "/some/random/path"
          ];
          config = { };
        };

      virtualisation.additionalPaths = [ pkgs.stdenv ];
    };

  testScript = ''
      machine.wait_for_unit("default.target")
      assert "tmpfs" in machine.succeed("nixos-container list")

      with subtest("tmpfs container is up"):
          assert "up" in machine.succeed("nixos-container status tmpfs")


      def tmpfs_cmd(command):
          return f"nixos-container run tmpfs -- {command} 2>/dev/null"


      with subtest("/var is mounted as a tmpfs"):
          machine.succeed(tmpfs_cmd("mountpoint -q /var"))

      with subtest("/var/log is mounted as a tmpfs"):
          assert "What: tmpfs" in machine.succeed(
              tmpfs_cmd("systemctl status var-log.mount --no-pager")
          )
          machine.succeed(tmpfs_cmd("mountpoint -q /var/log"))

      with subtest("/some/random/path is mounted as a tmpfs"):
          assert "What: tmpfs" in machine.succeed(
              tmpfs_cmd("systemctl status some-random-path.mount --no-pager")
          )
          machine.succeed(tmpfs_cmd("mountpoint -q /some/random/path"))

      with subtest(
          "files created in the container in a non-tmpfs directory are visible on the host."
      ):
          # This establishes legitimacy for the following tests
          machine.succeed(
              tmpfs_cmd("touch /root/test.file"),
              tmpfs_cmd("ls -l  /root | grep -q test.file"),
              "test -e /var/lib/containers/tmpfs/root/test.file",
          )

      with subtest(
          "/some/random/path is writable and that files created there are not "
          + "in the hosts container dir but in the tmpfs"
      ):
          machine.succeed(
              tmpfs_cmd("touch /some/random/path/test.file"),
              tmpfs_cmd("test -e /some/random/path/test.file"),
          )
          machine.fail("test -e /var/lib/containers/tmpfs/some/random/path/test.file")

      with subtest(
          "files created in the hosts container dir in a path where a tmpfs "
          + "file system has been mounted are not visible to the container as "
          + "the do not exist in the tmpfs"
      ):
          machine.succeed(
              "touch /var/lib/containers/tmpfs/var/test.file",
              "test -e /var/lib/containers/tmpfs/var/test.file",
              "ls -l /var/lib/containers/tmpfs/var/ | grep -q test.file 2>/dev/null",
          )
          machine.fail(tmpfs_cmd("ls -l /var | grep -q test.file"))
    '';
})