fix: only do LXD compat checks on Ubuntu

Signed-off-by: Sergio Schvezov <sergio.schvezov@canonical.com>

Author: Sergio Schvezov

craft_providers/bases/checks.py

@@ -1,5 +1,5 @@
 #
-# Copyright 2021-2023 Canonical Ltd.
+# Copyright 2021-2025 Canonical Ltd.
 #
 # This program is free software; you can redistribute it and/or
 # modify it under the terms of the GNU Lesser General Public
@@ -77,13 +77,24 @@ def ensure_guest_compatible(
     """Ensure host is compatible with guest instance."""
     if not issubclass(type(base_configuration), BuilddBase):
         # Not ubuntu, not sure how to check
+        logger.debug(
+            f"Base alias configuration is {base_configuration.alias!r}: no checks for non Buildd"
+        )
         return
 
+    host_os_release = parse_os_release()
+    # Return early for non Ubuntu hosts
+    if host_os_release.get("ID") != "ubuntu":
+        logger.debug(
+            f"Host is {host_os_release.get('ID')}: no checks for non Ubuntu hosts"
+        )
+        return
+
+    host_base_alias = BuilddBaseAlias(host_os_release.get("VERSION_ID"))
+
     guest_os_release = base_configuration._get_os_release(executor=instance)
     guest_base_alias = BuilddBaseAlias(guest_os_release.get("VERSION_ID"))
 
-    host_base_alias = BuilddBaseAlias(parse_os_release().get("VERSION_ID"))
-
     # Strip off anything after the first space - sometimes "LTS" is appended
     lxd_version_split = lxd_version.strip().split(" ")[0].split(".")
     lxd_major = int(lxd_version_split[0])

docs/reference/changelog.rst

@@ -4,12 +4,14 @@ Changelog
 See the `Releases page`_ on GitHub for a complete list of commits that are
 included in each version.
 
-2.3.1 (2025-Jun-05)
+2.3.1 (2025-Jun-19)
 -------------------
 
 Bug fixes:
 
 - Warn, but don't fail, on failures to mount a shared cache.
+- Fix issue where LXD failed to launch on non-Ubuntu distributions because
+  all OS identities were interpreted as Ubuntu versions.
 
 2.3.0 (2025-May-09)
 -------------------

tests/unit/bases/test_ensure_guest_compatible.py

@@ -37,6 +37,40 @@ def test_ensure_guest_compatible_not_ubuntu(fake_executor, fake_process):
     base._get_os_release.assert_not_called()
 
 
+def test_ensure_guest_compatible_non_ubuntu_host(
+    fake_executor,
+    fake_process,
+):
+    """Check for combinations of host and guest OS unaffected by the lxd issue."""
+    guest_base = ubuntu.BuilddBase(alias=ubuntu.BuilddBaseAlias.JAMMY)
+    guest_base._get_os_release = MagicMock(spec=guest_base._get_os_release)
+
+    # Mock the host os-release file
+    fake_process.register_subprocess(
+        [*DEFAULT_FAKE_CMD, "cat", "/etc/os-release"],
+        stdout='ID="fedora"',
+    )
+
+    # Mock the host os-release file contents
+    @contextlib.contextmanager
+    def fake_open(*args, **kwargs):
+        class Fake:
+            def read(self):
+                return 'ID="fedora"'
+
+        yield Fake()
+
+    with (
+        patch.object(craft_providers.util.os_release.Path, "open", fake_open),  # type: ignore[reportAttributeAccessIssue]
+    ):
+        ensure_guest_compatible(guest_base, fake_executor, "4.0")
+
+    # The first thing that ensure_guest_compatible does is the base check.  The next
+    # thing is to call _get_os_release on the base.  So if that isn't called then we
+    # haven't progressed.
+    guest_base._get_os_release.assert_not_called()
+
+
 @pytest.mark.parametrize(
     "base_alias",
     [
@@ -69,6 +103,7 @@ def fake_get_os_release(*args, **kwargs):
     # Mock the host os-release file
     fake_os_release = textwrap.dedent(
         f"""\
+        ID="ubuntu"
         VERSION_ID="{base_alias.value}"
         WOOP="dedoo"
         """
@@ -83,7 +118,12 @@ def fake_get_os_release(*args, **kwargs):
     def fake_open(*args, **kwargs):
         class Fake:
             def read(self):
-                return f'VERSION_ID="{base_alias.value}"'
+                return textwrap.dedent(
+                    f"""\
+                    ID="ubuntu"
+                    VERSION_ID="{base_alias.value}"
+                    """
+                )
 
         yield Fake()
 
@@ -147,7 +187,12 @@ def test_ensure_guest_compatible_bad_kernel_versions(
     def fake_open(*args, **kwargs):
         class Fake:
             def read(self):
-                return f'VERSION_ID="{host_base_alias.value}"'
+                return textwrap.dedent(
+                    f"""\
+                    ID="ubuntu"
+                    VERSION_ID="{host_base_alias.value}"
+                    """
+                )
 
         yield Fake()