cloud-id: publish /run/cloud-init/cloud-id-<cloud-type> files (#1244)

Once a valid datasource is detected, publish the following artifacts
to expedite cloud-identification without having to invoke cloud-id from
shell scripts or sheling out from python.
    
These files can also be relied on in systemd ConditionPathExists
directives to limit execution of services and units to specific
clouds.
    
/run/cloud-init/cloud-id:
 - A symlink with content that is the canonical cloud-id of the
   datasource detected. This content is the same lower-case value
   as the output of /usr/bin/cloud-id.

/run/cloud-init/cloud-id-<canonical-cloud-id>:
 - A single file which will contain the canonical cloud-id encoded
   in the filename

1 files changed, 26 insertions, 0 deletions

diff --git a/tests/integration_tests/modules/test_combined.py b/tests/integration_tests/modules/test_combined.py
index 43aa809e..7a9a6e27 100644
--- a/tests/integration_tests/modules/test_combined.py
+++ b/tests/integration_tests/modules/test_combined.py
@@ -222,6 +222,16 @@ class TestCombined:
                 == parsed_datasource
             )
 
+    def test_cloud_id_file_symlink(self, class_client: IntegrationInstance):
+        cloud_id = class_client.execute("cloud-id").stdout
+        expected_link_output = (
+            "'/run/cloud-init/cloud-id' -> "
+            f"'/run/cloud-init/cloud-id-{cloud_id}'"
+        )
+        assert expected_link_output == str(
+            class_client.execute("stat -c %N /run/cloud-init/cloud-id")
+        )
+
     def _check_common_metadata(self, data):
         assert data["base64_encoded_keys"] == []
         assert data["merged_cfg"] == "redacted for non-root user"
@@ -249,6 +259,10 @@ class TestCombined:
         v1_data = data["v1"]
         assert v1_data["cloud_name"] == "unknown"
         assert v1_data["platform"] == "lxd"
+        assert v1_data["cloud_id"] == "lxd"
+        assert f"{v1_data['cloud_id']}" == client.read_from_file(
+            "/run/cloud-init/cloud-id-lxd"
+        )
         assert (
             v1_data["subplatform"]
             == "seed-dir (/var/lib/cloud/seed/nocloud-net)"
@@ -270,6 +284,10 @@ class TestCombined:
         v1_data = data["v1"]
         assert v1_data["cloud_name"] == "unknown"
         assert v1_data["platform"] == "lxd"
+        assert v1_data["cloud_id"] == "lxd"
+        assert f"{v1_data['cloud_id']}" == client.read_from_file(
+            "/run/cloud-init/cloud-id-lxd"
+        )
         assert any(
             [
                 "/var/lib/cloud/seed/nocloud-net" in v1_data["subplatform"],
@@ -291,6 +309,11 @@ class TestCombined:
         v1_data = data["v1"]
         assert v1_data["cloud_name"] == "aws"
         assert v1_data["platform"] == "ec2"
+        # Different regions will show up as ec2-(gov|china)
+        assert v1_data["cloud_id"].startswith("ec2")
+        assert f"{v1_data['cloud_id']}" == client.read_from_file(
+            "/run/cloud-init/cloud-id-ec2"
+        )
         assert v1_data["subplatform"].startswith("metadata")
         assert (
             v1_data["availability_zone"] == client.instance.availability_zone
@@ -310,6 +333,9 @@ class TestCombined:
         v1_data = data["v1"]
         assert v1_data["cloud_name"] == "gce"
         assert v1_data["platform"] == "gce"
+        assert f"{v1_data['cloud_id']}" == client.read_from_file(
+            "/run/cloud-init/cloud-id-gce"
+        )
         assert v1_data["subplatform"].startswith("metadata")
         assert v1_data["availability_zone"] == client.instance.zone
         assert v1_data["instance_id"] == client.instance.instance_id