Merge pull request #737 from ftyghome/feat_rootfs

Support podman's external rootfs management

docs/Extensions.md

@@ -65,3 +65,27 @@ In addition, podman-compose supports the following podman-specific values for `n
 
 The options to the network modes are passed to the `--network` option of the `podman create` command
 as-is.
+
+# Service management
+
+Podman-compose extends the compose specification to support some unique features of Podman. These extensions can be specified in the compose file under the "x-podman" field.
+
+Currently, podman-compose supports the following extensions:
+
+* `uidmap` - Run the container in a new user namespace using the supplied UID mapping.
+
+* `gidmap` - Run the container in a new user namespace using the supplied GID mapping.
+
+* `rootfs` - Run the container without requiring any image management; the rootfs of the container is assumed to be managed externally.
+
+For example, the following docker-compose.yml allows running a podman container with externally managed rootfs.
+```yml
+version: "3"
+services:
+    my_service:
+      command: ["/bin/busybox"]
+      x-podman:
+        rootfs: "/path/to/rootfs"
+```
+
+For explanations of these extensions, please refer to the [Podman Documentation](https://docs.podman.io/).

podman_compose.py

@@ -1145,13 +1145,23 @@ async def container_to_args(compose, cnt, detached=True):
 
     # handle podman extension
     x_podman = cnt.get("x-podman", None)
+    rootfs_mode = False
     if x_podman is not None:
         for uidmap in x_podman.get("uidmaps", []):
             podman_args.extend(["--uidmap", uidmap])
         for gidmap in x_podman.get("gidmaps", []):
             podman_args.extend(["--gidmap", gidmap])
+        rootfs = x_podman.get("rootfs", None)
+        if rootfs is not None:
+            rootfs_mode = True
+            podman_args.extend(["--rootfs", rootfs])
+            log.warning(
+                "WARNING: x-podman.rootfs and image both specified, \
+            image field ignored"
+            )
 
-    podman_args.append(cnt["image"])  # command, ..etc.
+    if not rootfs_mode:
+        podman_args.append(cnt["image"])  # command, ..etc.
     command = cnt.get("command", None)
     if command is not None:
         if is_str(command):
@@ -1831,7 +1841,9 @@ class PodmanCompose:
                     "service_name": service_name,
                     **service_desc,
                 }
-                if "image" not in cnt:
+                x_podman = service_desc.get("x-podman", None)
+                rootfs_mode = x_podman is not None and x_podman.get("rootfs", None) is not None
+                if "image" not in cnt and not rootfs_mode:
                     cnt["image"] = f"{project_name}_{service_name}"
                 labels = norm_as_list(cnt.get("labels", None))
                 cnt["ports"] = norm_ports(cnt.get("ports", None))

pytests/test_container_to_args.py

@@ -161,3 +161,25 @@ class TestContainerToArgs(unittest.IsolatedAsyncioTestCase):
                 "busybox",
             ],
         )
+
+    async def test_rootfs_extension(self):
+        c = create_compose_mock()
+
+        cnt = get_minimal_container()
+        del cnt["image"]
+        cnt["x-podman"] = {
+            "rootfs": "/path/to/rootfs",
+        }
+
+        args = await container_to_args(c, cnt)
+        self.assertEqual(
+            args,
+            [
+                "--name=project_name_service_name1",
+                "-d",
+                "--network=bridge",
+                "--network-alias=service_name",
+                "--rootfs",
+                "/path/to/rootfs",
+            ],
+        )