Keep x11vnc alive for remote login

docker/entrypoint.sh

@@ -54,7 +54,7 @@ if command -v fluxbox >/dev/null 2>&1; then
   fluxbox >/dev/null 2>&1 &
 fi
 
-VNC_ARGS=(-display "${DISPLAY}" -forever -shared -rfbport "${VNC_PORT}" -nopw_warn)
+VNC_ARGS=(-display "${DISPLAY}" -forever -shared -rfbport "${VNC_PORT}")
 if [ -n "${VNC_PASSWORD:-}" ]; then
   mkdir -p /root/.vnc
   x11vnc -storepasswd "${VNC_PASSWORD}" /root/.vnc/passwd >/dev/null
@@ -68,6 +68,27 @@ fi
 x11vnc "${VNC_ARGS[@]}" >/var/log/x11vnc.log 2>&1 &
 X11VNC_PID=$!
 
+VNC_READY=0
+for i in $(seq 1 50); do
+  if ! kill -0 "${X11VNC_PID}" 2>/dev/null; then
+    echo "[entrypoint] FATAL: x11vnc exited before becoming ready" >&2
+    cat /var/log/x11vnc.log >&2
+    exit 1
+  fi
+  if (: </dev/tcp/127.0.0.1/${VNC_PORT}) 2>/dev/null; then
+    echo "[entrypoint] VNC server is ready after ${i} checks"
+    VNC_READY=1
+    break
+  fi
+  sleep 0.2
+done
+
+if [ "${VNC_READY}" != "1" ]; then
+  echo "[entrypoint] FATAL: x11vnc did not listen on port ${VNC_PORT} after 10s" >&2
+  cat /var/log/x11vnc.log >&2
+  exit 1
+fi
+
 echo "[entrypoint] starting noVNC (websockify) on :${NOVNC_PORT}"
 websockify --web "${NOVNC_WEB_DIR}" "${NOVNC_PORT}" "localhost:${VNC_PORT}" \
   >/var/log/websockify.log 2>&1 &