feat: prototype approach without loopback executor

craft_providers/bases/ubuntu.py

@@ -35,6 +35,7 @@
 )
 from craft_providers.executor import Executor
 from craft_providers.loopback_executor import LoopbackExecutor
+from craft_providers.util.os_release import parse_os_release
 
 logger = logging.getLogger(__name__)
 
@@ -300,8 +301,13 @@ def ensure_guest_compatible(base_configuration: Base, guest_instance: Executor)
     # _get_os_release, which uses timeout values from the base_configuration instance and
     # nothing else.
     guest_base_alias = _get_buildd_base_alias(base_configuration, guest_instance)
+
+    # With loopback executor:
     host_base_alias = _get_buildd_base_alias(base_configuration, host_instance)
 
+    # Without loopback executor:
+    host_base_alias = BuilddBaseAlias(parse_os_release().get("VERSION_ID"))
+
     # If the host OS is focal (20.04) or older, and the guest OS is oracular (24.10)
     # or newer, then the host lxd must be >=5.0.4 or >=5.21.2, and kernel must be
     # 5.15 or newer.  Otherwise, weird systemd failures will occur due to a mismatch

craft_providers/util/os_release.py

@@ -16,10 +16,14 @@
 #
 
 """Parser for /etc/os-release."""
+
+from pathlib import Path
 from typing import Dict
 
+OS_RELEASE_FILE = Path("/etc/os-release")
+
 
-def parse_os_release(content: str) -> Dict[str, str]:
+def parse_os_release(content: str | None) -> Dict[str, str]:
     """Parser for /etc/os-release.
 
     Format documentation at:
@@ -41,12 +45,17 @@ def parse_os_release(content: str) -> Dict[str, str]:
         VERSION_CODENAME=jammy
         UBUNTU_CODENAME=jammy
 
-    :param content: String contents of os-release file.
+    :param content: String contents of os-release file.  If None, will read contents of
+    file from host.
 
     :returns: Dictionary of key-mappings found in os-release. Values are
-              stripped of encapsulating quotes.
+    stripped of encapsulating quotes.
 
     """
+    if content is None:
+        with OS_RELEASE_FILE.open() as f:
+            content = f.read()
+
     mappings: Dict[str, str] = {}
 
     for line in content.splitlines():