proper terminate all background processes in ucind containers

Dockerfile

@@ -35,6 +35,7 @@ RUN apk --no-cache add crane
 RUN crane pull "${CORROSION_IMAGE}" /corrosion.tar
 
 
+# Uncloud-in-Docker (ucind) image for running Uncloud test clusters using Docker.
 FROM docker:27.3.1-dind AS ucind
 # Create system group and user 'uncloud'.
 RUN addgroup -S uncloud && adduser -SHD -h /nonexistent -G uncloud -g "" uncloud

scripts/docker/entrypoint.sh

@@ -1,7 +1,28 @@
 #!/bin/sh
 set -eu
 
-# TODO: cleanup /run/docker.pid on exit to support container restart.
+# Cleanup function to properly terminate background processes.
+cleanup() {
+    echo "Terminating container processes..."
+
+    # Terminate the main process if it has been started.
+    if [ -n "$MAIN_PID" ]; then
+        kill "$MAIN_PID" 2>/dev/null || true
+    fi
+
+    # Terminate Docker daemon if PID file exists.
+    if [ -f /run/docker.pid ]; then
+        kill "$(cat /run/docker.pid)" 2>/dev/null || true
+    fi
+
+    # Terminate socat proxy if running.
+    pkill socat 2>/dev/null || true
+
+    # Wait for processes to terminate.
+    wait
+}
+trap cleanup INT TERM
+
 dind dockerd &
 echo "Waiting for Docker in Docker to be ready..."
 timeout 5s sh -c "until docker info &> /dev/null; do sleep 0.1; done"
@@ -14,4 +35,7 @@ docker load < /images/corrosion.tar
 echo "Proxying Uncloud API port 51000/tcp to Unix socket /run/uncloud/uncloud.sock..."
 socat TCP-LISTEN:51000,reuseaddr,fork,bind="$(hostname -i)" UNIX-CONNECT:/run/uncloud/uncloud.sock &
 
-exec "$@"
+# Execute the passed command and wait for it while maintaining signal handling.
+"$@" &
+MAIN_PID=$!
+wait $MAIN_PID