# Issue when launching ROS with PX4 SITL after successful Gazebo simulation

**URL:** <https://discuss.px4.io/t/issue-when-launching-ros-with-px4-sitl-after-successful-gazebo-simulation/45529>\
**Category:** Uncategorized\
**Created:** [May 13, 2025, 2:04pm UTC](https://discuss.px4.io/t/issue-when-launching-ros-with-px4-sitl-after-successful-gazebo-simulation/45529 "2025-05-13T14:04:22Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![yizhezhang0418](https://discuss.px4.io/user_avatar/discuss.px4.io/yizhezhang0418/32/19382_2.png) [@yizhezhang0418](https://discuss.px4.io/u/yizhezhang0418)\
**Post date:** [May 13, 2025, 2:04pm UTC](https://discuss.px4.io/t/issue-when-launching-ros-with-px4-sitl-after-successful-gazebo-simulation/45529/1 "2025-05-13T14:04:22Z")

</div>

Hi everyone,

I’m encountering an issue while trying to run PX4 SITL using ROS.

Here’s the scenario:

1. I successfully compiled PX4 with the command:

```auto
> make px4_sitl_default gazebo

```

This command launches the simulation, and I can see the drone in Gazebo, and I am able to control and fly it without any problems.

1. However, when I try to launch the ROS interface with the command:

```auto
> roslaunch px4 posix_sitl.launch

```

I get the following error message:

```auto
> (base) ljp@ljp-MS-7E25:~/PX4-Autopilot$ roslaunch px4 posix_sitl.launch 
... logging to /home/ljp/.ros/log/e545ea38-2ffe-11f0-9b8d-ab0902c6161d/roslaunch-ljp-MS-7E25-206641.log
Checking log directory for disk usage. This may take a while.
Press Ctrl-C to interrupt
WARNING: disk usage in log directory [/home/ljp/.ros/log] is over 1GB.
It's recommended that you use the 'rosclean' command.

started roslaunch server http://ljp-MS-7E25:33455/

SUMMARY
========

PARAMETERS
 * /gazebo/enable_ros_network: True
 * /rosdistro: noetic
 * /rosversion: 1.17.0
 * /use_sim_time: True

NODES
  /
    gazebo (gazebo_ros/gzserver)
    gazebo_gui (gazebo_ros/gzclient)
    sitl (px4/px4)
    vehicle_spawn_ljp_MS_7E25_206641_4875867567744766849 (gazebo_ros/spawn_model)

ROS_MASTER_URI=http://localhost:11311

process[sitl-1]: started with pid [206712]
process[gazebo-2]: started with pid [206713]
process[gazebo_gui-3]: started with pid [206717]
process[vehicle_spawn_ljp_MS_7E25_206641_4875867567744766849-4]: started with pid [206722]
================================================================================REQUIRED process [sitl-1] has died!
process has died [pid 206712, exit code 255, cmd /home/ljp/PX4-Autopilot/build/px4_sitl_default/bin/px4 /home/ljp/PX4-Autopilot/build/px4_sitl_default/etc -s etc/init.d-posix/rcS __name:=sitl__ log:=/home/ljp/.ros/log/e545ea38-2ffe-11f0-9b8d-ab0902c6161d/sitl-1.log].
log file: /home/ljp/.ros/log/e545ea38-2ffe-11f0-9b8d-ab0902c6161d/sitl-1*.log
Initiating shutdown!
================================================================================
[vehicle_spawn_ljp_MS_7E25_206641_4875867567744766849-4] killing on exit
[gazebo_gui-3] killing on exit
[gazebo-2] killing on exit
[sitl-1] killing on exit
Traceback (most recent call last):
  File "/opt/ros/noetic/lib/gazebo_ros/spawn_model", line 20, in <module>
    import rospy
  File "/opt/ros/noetic/lib/python3/dist-packages/rospy/ __init__.py", line 49, in <module>
    from .client import spin, myargv, init_node, \
  File "/opt/ros/noetic/lib/python3/dist-packages/rospy/client.py", line 49, in <module>
    import rosgraph
  File "/opt/ros/noetic/lib/python3/dist-packages/rosgraph/ __init__.py", line 36, in <module>
    from . masterapi import Master, MasterFailure, MasterError, MasterException
  File "/opt/ros/noetic/lib/python3/dist-packages/rosgraph/masterapi.py", line 41, in <module>
    from xmlrpc.client import ServerProxy # Python 3.x
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/ljp/miniconda3/lib/python3.12/xmlrpc/client.py", line 136, in <module>
    import http.client
  File "/home/ljp/miniconda3/lib/python3.12/http/client.py", line 71, in <module>
    import email.parser
  File "/home/ljp/miniconda3/lib/python3.12/email/parser.py", line 12, in <module>
    from email.feedparser import FeedParser, BytesFeedParser
  File "/home/ljp/miniconda3/lib/python3.12/email/feedparser.py", line 27, in <module>
    from email._policybase import compat32
  File "/home/ljp/miniconda3/lib/python3.12/email/_policybase.py", line 7, in <module>
    from email import header
  File "/home/ljp/miniconda3/lib/python3.12/email/header.py", line 20, in <module>
    from email import charset as _charset
  File "/home/ljp/miniconda3/lib/python3.12/email/charset.py", line 18, in <module>
    from email.encoders import encode_7or8bit
KeyboardInterrupt
shutting down processing monitor...
... shutting down processing monitor complete
done

```

I have already set the necessary paths in my `.bashrc` file, but the issue persists.

Could anyone help me understand what might be causing this issue or suggest a solution? I’m unsure why the Gazebo simulation works fine, but ROS fails to launch.

Thanks in advance for your help!

---

<div class="post-metadata">

**Author:** ![rroche](https://discuss.px4.io/user_avatar/discuss.px4.io/rroche/32/17635_2.png) [@rroche](https://discuss.px4.io/u/rroche)\
**Post date:** [May 13, 2025, 3:48pm UTC](https://discuss.px4.io/t/issue-when-launching-ros-with-px4-sitl-after-successful-gazebo-simulation/45529/2 "2025-05-13T15:48:22Z")

</div>

have you tried inspecting the ROS log to see what went wrong? from your code above here’s the path:

> /home/ljp/.ros/log/e545ea38-2ffe-11f0-9b8d-ab0902c6161d/sitl-1\*.log