feat(core): find ss executable path by OS ID (#12)

Executables were run through hardcoded absolute paths, it only works on some distributions.
`ss` is in `/usr/bin` on the GitHub Ubuntu runners, instead of in `/usr/sbin`
on XCP-ng so the LINSTOR controller tests are marked as failed.

Now "/etc/os-release" is used to find alternate OS specific paths instead.

Signed-off-by: Ronan Abhamon <ronan.abhamon@vates.tech>

Author: Wescoeur

src/xcp_storage/backends/linstor/controller.py

@@ -13,6 +13,7 @@
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 from xcp_storage.backends.linstor.satellite import LINSTOR_SATELLITE_PORT_PLAIN, LINSTOR_SATELLITE_PORT_SSL
+from xcp_storage.config.platform import get_exec_path
 from xcp_storage.utils.process import run_command
 from xcp_storage.utils.service import (
     is_service_active,
@@ -30,7 +31,7 @@
 
 # ------------------------------------------------------------------------------
 
-_EXEC_PATH_SS: Final = "/usr/sbin/ss"
+_EXEC_PATH_SS: Final = get_exec_path("/usr/sbin/ss", {"debian": "/usr/bin/ss"})
 
 _SERVICE_LINSTOR_CONTROLLER: Final = "linstor-controller"
 

src/xcp_storage/config/platform.py

@@ -12,7 +12,10 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
-from xcp_storage.typing import Final
+from functools import lru_cache
+from pathlib import Path
+
+from xcp_storage.typing import Final, Mapping, Tuple
 
 # ==============================================================================
 # Attributes that depend on the execution environment.
@@ -21,3 +24,35 @@
 # ==============================================================================
 
 DEFAULT_FIREWALL_INPUT_CHAIN: Final = "xapi-INPUT"
+
+# ------------------------------------------------------------------------------
+
+_OS_RELEASE_PATH: Final = "/etc/os-release"
+
+@lru_cache(maxsize=None)
+def get_os_ids() -> Tuple[str, ...]:
+    """
+    Get the IDs of the current distribution, most specific first: `ID` followed
+    by the values of `ID_LIKE` (e.g. `("ubuntu", "debian")`). The result is
+    cached. An empty tuple is returned if `/etc/os-release` can't be read.
+    """
+
+    try:
+        lines = Path(_OS_RELEASE_PATH).read_text(encoding="utf-8").splitlines()
+    except OSError:
+        return ()
+
+    values = {}
+    for line in lines:
+        key, _separator, value = line.partition("=")
+        values[key.strip()] = value.strip().strip("\"'")
+
+    return tuple(values.get("ID", "").split() + values.get("ID_LIKE", "").split())
+
+def get_exec_path(default: str, by_os_id: Mapping[str, str]) -> str:
+    """
+    Get the path of an executable: the one registered for the first matching OS
+    ID, otherwise `default`.
+    """
+
+    return next((by_os_id[os_id] for os_id in get_os_ids() if os_id in by_os_id), default)

tests/config/test_platform.py

@@ -0,0 +1,82 @@
+# Copyright (C) 2026  Vates SAS
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+from pathlib import Path
+from unittest.mock import patch
+
+import pytest
+
+from xcp_storage.config.platform import get_exec_path, get_os_ids
+
+from xcp_storage.typing import Final, Iterator, Tuple
+
+# ==============================================================================
+
+@pytest.fixture(autouse=True)
+def clear_os_ids_cache() -> Iterator[None]:
+    get_os_ids.cache_clear()
+    yield
+    get_os_ids.cache_clear()
+
+@pytest.fixture
+def os_release_path(tmp_path: Path) -> Iterator[Path]:
+    path = tmp_path / "os-release"
+    with patch("xcp_storage.config.platform._OS_RELEASE_PATH", str(path)):
+        yield path
+
+# ------------------------------------------------------------------------------
+
+class TestGetOsIds:
+    @pytest.mark.parametrize(("content", "expected"), [
+        ("ID=alpine\n", ("alpine",)),
+        ('NAME="Ubuntu"\nID=ubuntu\nID_LIKE=debian\n', ("ubuntu", "debian")),
+        ('ID="rhel"\nID_LIKE="fedora centos"\n', ("rhel", "fedora", "centos")),
+        ("NAME=Foo\n", ()),
+    ])
+    def test_parsing(self, os_release_path: Path, content: str, expected: Tuple[str, ...]) -> None:
+        os_release_path.write_text(content)
+        assert get_os_ids() == expected
+
+    def test_without_os_release_file(self, os_release_path: Path) -> None:
+        assert not os_release_path.exists()
+        assert get_os_ids() == ()
+
+    def test_os_release_file_is_cached(self, os_release_path: Path) -> None:
+        os_release_path.write_text("ID=alpine\n")
+        expected = get_os_ids()
+        os_release_path.write_text("ID=ubuntu\n")
+        assert get_os_ids() == expected
+
+# ------------------------------------------------------------------------------
+
+class TestGetExecPath:
+    DEFAULT_PATH: Final = "/opt/default/tool"
+    ALT_PATH: Final = "/opt/alt/tool"
+    BY_OS_ID: Final = {"debian": ALT_PATH}
+
+    def test_with_mapping_id_match(self, os_release_path: Path) -> None:
+        os_release_path.write_text("ID=debian\nID_LIKE=unknown\n")
+        assert get_exec_path(self.DEFAULT_PATH, self.BY_OS_ID) == self.ALT_PATH
+
+    def test_with_mapping_id_like_match(self, os_release_path: Path) -> None:
+        os_release_path.write_text("ID=ubuntu\nID_LIKE=debian\n")
+        assert get_exec_path(self.DEFAULT_PATH, self.BY_OS_ID) == self.ALT_PATH
+
+    def test_without_mapping_match(self, os_release_path: Path) -> None:
+        os_release_path.write_text("ID=alpine\n")
+        assert get_exec_path(self.DEFAULT_PATH, self.BY_OS_ID) == self.DEFAULT_PATH
+
+    def test_without_os_release_file(self, os_release_path: Path) -> None:
+        assert not os_release_path.exists()
+        assert get_exec_path(self.DEFAULT_PATH, self.BY_OS_ID) == self.DEFAULT_PATH