DEVX-24: fix: use separate Docker socket for DinD in CI

src/devx/molecule/start_docker.py

@@ -3,8 +3,9 @@
 
 CI runners (e.g. ``gitea/runner-images:ubuntu-latest``) may have the host's
 Docker socket mounted, but molecule needs a local Docker daemon to create
-nested containers. This module always starts ``dockerd`` in the background
-and waits for it to become ready.
+nested containers. This module starts ``dockerd`` on a separate socket
+and sets ``DOCKER_HOST`` so both the CLI and Python library connect to
+the local daemon.
 
 Usage::
 
@@ -13,6 +14,7 @@ Usage::
 
 from __future__ import annotations
 
+import os
 import subprocess  # nosec B404
 import sys
 import tempfile
@@ -23,34 +25,46 @@ import click
 from devx.i18n import _
 
 DEFAULT_TIMEOUT = 30
+DOCKER_SOCK = "/tmp/dockerd.sock"  # nosec B108
 
 
 def is_docker_ready() -> bool:
-    """Check if the Docker daemon is responding."""
+    """Check if the local Docker daemon is responding."""
     result = subprocess.run(  # nosec B603 B607
         ["docker", "info"],
         capture_output=True,
         check=False,
+        env={**os.environ, "DOCKER_HOST": f"unix://{DOCKER_SOCK}"},
     )
     return result.returncode == 0
 
 
 def start_docker_daemon(timeout: int = DEFAULT_TIMEOUT) -> bool:
-    """Start dockerd in the background and wait for it to be ready.
+    """Start dockerd on a separate socket and wait for it to be ready.
 
-    Always starts a local dockerd even if ``docker info`` succeeds,
-    because the host socket may be mounted but not suitable for
-    molecule's nested container creation.
+    Uses ``/tmp/dockerd.sock`` instead of the default ``/var/run/docker.sock``
+    to avoid conflicts with host-mounted sockets. Sets ``DOCKER_HOST`` in the
+    current environment so molecule's Python docker library connects to the
+    local daemon.
 
     Returns ``True`` if Docker is ready, ``False`` if it failed to
     start within the timeout.
     """
+    # Point Docker CLI and Python library to our local socket
+    os.environ["DOCKER_HOST"] = f"unix://{DOCKER_SOCK}"
+
     click.echo(_("Starting Docker daemon..."))
     log_file = tempfile.NamedTemporaryFile(  # noqa: SIM115
         mode="w", suffix="dockerd.log", delete=False
     )
     subprocess.Popen(  # nosec B603 B607
-        ["dockerd", "--storage-driver", "vfs"],
+        [
+            "dockerd",
+            "--storage-driver",
+            "vfs",
+            "-H",
+            f"unix://{DOCKER_SOCK}",
+        ],
         stdout=log_file,
         stderr=subprocess.STDOUT,
         start_new_session=True,