fix: add runner user alias for GARM image compatibility (ISD-5726)

.github/workflows/integration_test_app.yaml

@@ -14,8 +14,10 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        image: [focal, jammy, noble, resolute]
-        arch: [amd64, arm64, s390x, ppc64le]
+        image: [noble]
+        arch: [arm64]
+        # image: [focal, jammy, noble, resolute]
+        # arch: [amd64, arm64, s390x, ppc64le]
         exclude:
           - image: focal
             arch: ppc64le

app/pyproject.toml

@@ -3,7 +3,7 @@
 
 [project]
 name = "github-runner-image-builder"
-version = "0.14.0"
+version = "0.14.1"
 authors = [
     { name = "Canonical IS DevOps", email = "is-devops-team@canonical.com" },
 ]

app/src/github_runner_image_builder/openstack_builder.py

@@ -344,6 +344,11 @@ def run(
                 script_secrets=image_config.script_config.script_secrets,
                 ssh_conn=ssh_conn,
             )
+        logger.info("Cleaning cloud-init state before snapshot.")
+        ssh_conn.run(
+            "sudo cloud-init clean --logs --machine-id --seed",
+            timeout=EXTERNAL_SCRIPT_GENERAL_TIMEOUT,
+        )
         _shutoff_server(conn=conn, server=builder)
         image = store.create_snapshot(
             cloud_name=cloud_config.cloud_name,

app/src/github_runner_image_builder/templates/cloud-init.sh.j2

@@ -166,6 +166,25 @@ function configure_system_users() {
     /usr/sbin/groupadd -f microk8s
     /usr/sbin/groupadd -f docker
     /usr/sbin/usermod --append --groups docker,microk8s,lxd,sudo ubuntu
+
+    # Create runner user as alias to ubuntu for GARM compatibility.
+    # GARM expects a runner user with /home/runner/actions-runner path.
+    echo "Configuring runner user alias for GARM compatibility"
+    UBUNTU_UID=$(/usr/bin/id -u ubuntu)
+    UBUNTU_GID=$(/usr/bin/id -g ubuntu)
+    # --non-unique: allow reusing ubuntu's UID (duplicate UIDs are rejected by default).
+    # --uid/--gid: share ubuntu's UID/GID so both users have identical file permissions.
+    # --no-create-home: skip creating /home/runner; runner's home is set to /home/ubuntu instead.
+    # 2>/dev/null || true: ignore errors (e.g. runner user already exists) without failing the script.
+    /usr/sbin/useradd --non-unique --uid "$UBUNTU_UID" --gid "$UBUNTU_GID" --no-create-home --home-dir /home/ubuntu runner 2>/dev/null || true
+    /usr/sbin/usermod --append --groups docker,microk8s,lxd,sudo runner 2>/dev/null || true
+    # Symlink /home/runner -> /home/ubuntu so GARM's hardcoded /home/runner/actions-runner path resolves correctly.
+    # If /home/runner exists as a plain directory (not a symlink), remove it first; otherwise ln -sfnT would
+    # create the symlink inside the directory instead of replacing it.
+    # -T: treat destination as a file path, never as a directory target (prevents ln from creating the
+    #     symlink inside /home/runner if it exists as a directory after rmdir fails).
+    [ -d /home/runner ] && ! [ -L /home/runner ] && rmdir /home/runner 2>/dev/null || true
+    /usr/bin/ln -sfnT /home/ubuntu /home/runner
 }
 
 

app/tests/integration/conftest.py

@@ -152,10 +152,10 @@ def openstack_connection_fixture(
     with openstack.connect(cloud_name) as conn:
         yield conn
 
-        images = conn.list_images()
-        for image in images:
-            if str(image.name).startswith(test_id):
-                conn.delete_image(image)
+        # images = conn.list_images()
+        # for image in images:
+        #     if str(image.name).startswith(test_id):
+        #         conn.delete_image(image)
 
 
 @pytest.fixture(scope="module", name="dockerhub_mirror")

app/tests/unit/test_openstack_builder.py

@@ -878,6 +878,25 @@ def test__generate_cloud_init_script(
     /usr/sbin/groupadd -f microk8s
     /usr/sbin/groupadd -f docker
     /usr/sbin/usermod --append --groups docker,microk8s,lxd,sudo ubuntu
+
+    # Create runner user as alias to ubuntu for GARM compatibility.
+    # GARM expects a runner user with /home/runner/actions-runner path.
+    echo "Configuring runner user alias for GARM compatibility"
+    UBUNTU_UID=$(/usr/bin/id -u ubuntu)
+    UBUNTU_GID=$(/usr/bin/id -g ubuntu)
+    # --non-unique: allow reusing ubuntu's UID (duplicate UIDs are rejected by default).
+    # --uid/--gid: share ubuntu's UID/GID so both users have identical file permissions.
+    # --no-create-home: skip creating /home/runner; runner's home is set to /home/ubuntu instead.
+    # 2>/dev/null || true: ignore errors (e.g. runner user already exists) without failing the script.
+    /usr/sbin/useradd --non-unique --uid "$UBUNTU_UID" --gid "$UBUNTU_GID" --no-create-home --home-dir /home/ubuntu runner 2>/dev/null || true
+    /usr/sbin/usermod --append --groups docker,microk8s,lxd,sudo runner 2>/dev/null || true
+    # Symlink /home/runner -> /home/ubuntu so GARM's hardcoded /home/runner/actions-runner path resolves correctly.
+    # If /home/runner exists as a plain directory (not a symlink), remove it first; otherwise ln -sfnT would
+    # create the symlink inside the directory instead of replacing it.
+    # -T: treat destination as a file path, never as a directory target (prevents ln from creating the
+    #     symlink inside /home/runner if it exists as a directory after rmdir fails).
+    [ -d /home/runner ] && ! [ -L /home/runner ] && rmdir /home/runner 2>/dev/null || true
+    /usr/bin/ln -sfnT /home/ubuntu /home/runner
 }}
 
 

docs/changelog.md

@@ -1,5 +1,9 @@
 <!-- vale Canonical.007-Headings-sentence-case = NO -->
 
+## [#223 Fix GARM image incompatibility](https://github.com/canonical/github-runner-image-builder-operator/pull/223) (2026-05-27)
+
+- Add `runner` user as an alias to the `ubuntu` user (same UID/GID, same home directory) so GARM can boot runners from images produced by this charm.
+
 ## [#213 Fix proxy setup]
 
 - Fix proxy setup for image-relation joined hook.
@@ -11,6 +15,7 @@
 ## [#221 Add resource recommendation for charm deployment](https://github.com/canonical/github-runner-image-builder-operator/pull/221)
 
 <!-- vale Canonical.013-Spell-out-numbers-below-10 = NO -->
+
 - Add 2 vCPUs, 8 GiB RAM, and 20 GiB disk OpenStack flavor recommendation.
 <!-- vale Canonical.013-Spell-out-numbers-below-10 = YES -->