Adding the ChrootManager class

Chroot manager class can be used to setup
a chroot enviroment including an arbitrary
list of bind mounts. The provided paths to bind
are mounted in the chroot to the same actual root
path they are bound from.

This class is useful to setup a chroot envirment
based on the root-tree created on prepare step.

Signed-off-by: David Cassany <[email protected]>

Author: davidcassany

kiwi/chroot_manager.py

@@ -0,0 +1,119 @@
+# Copyright (c) 2025 SUSE Software Solutions Germany GmbH.  All rights reserved.
+#
+# This file is part of kiwi.
+#
+# kiwi 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.
+#
+# kiwi 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 kiwi.  If not, see <http://www.gnu.org/licenses/>
+#
+import os
+import logging
+from typing import (
+    List, Optional
+)
+
+# project
+from kiwi.mount_manager import MountManager
+from kiwi.command import (
+  Command, CommandT, MutableMapping
+)
+from kiwi.exceptions import (
+    KiwiUmountBusyError
+)
+
+log = logging.getLogger('kiwi')
+
+
+class ChrootManager:
+    """
+    **Implements methods for setting and unsetting a chroot environment**
+
+    The caller is responsible for cleaning up bind mounts if the ChrootManager
+    is used as is.
+
+    The class also supports to be used as a context manager, where any bind or kernel
+    filesystem mount is unmounted once the context manager's with block is left
+
+    * :param string root_dir: path to change the root to
+    * :param list binds: current root paths to bind to the chrooted path
+    """
+    def __init__(self, root_dir: str, binds: List[str] = []):
+        self.root_dir = root_dir
+        self.mounts: List[MountManager] = []
+        for bind in binds:
+            self.mounts.append(MountManager(
+                device=bind, mountpoint=os.path.normpath(root_dir + bind)
+            ))
+
+    def __enter__(self) -> "ChrootManager":
+        try:
+            self.mount()
+        except Exception as e:
+            self.umount()
+            raise KiwiChrootEnterError(e)
+        return self
+
+    def __exit__(self, exc_type, exc_value, traceback) -> None:
+        self.umount()
+
+    def mount(self) -> None:
+        """
+        Mounts binds to the chroot path
+        """
+        for mnt in self.mounts:
+            mnt.bind_mount()
+
+    def umount(self) -> None:
+        """
+        Unmounts all binds from the chroot path
+
+        If any unmount raises a KiwiUmountBusyError this is trapped
+        and kept until the iteration over all bind mounts is over.
+        """
+        errors = []
+        for mnt in reversed(self.mounts):
+            try:
+                mnt.umount()
+            except KiwiUmountBusyError as e:
+                errors.append(e)
+
+        if errors:
+            raise KiwiUmountBusyError(errors)
+
+    def run(
+        self, command: List[str],
+        custom_env: Optional[MutableMapping[str, str]] = None,
+        raise_on_error: bool = True, stderr_to_stdout: bool = False,
+        raise_on_command_not_found: bool = True
+    ) -> Optional[CommandT]:
+        """
+        This is a wrapper for Command.run method but pre-appending the
+        chroot call at the command list
+
+        :param list command: command and arguments
+        :param dict custom_env: custom os.environ
+        :param bool raise_on_error: control error behaviour
+        :param bool stderr_to_stdout: redirects stderr to stdout
+
+        :return:
+            Contains call results in command type
+
+            .. code:: python
+
+                CommandT(output='string', error='string', returncode=int)
+
+        :rtype: CommandT
+        """
+        chroot_cmd = ['chroot', self.root_dir]
+        chroot_cmd = chroot_cmd + command
+        return Command.run(chroot_cmd)
+