# Revision history [back]

### roscore error, ROS_MASTER_URI

Hello! Everyone. I have encountered an roscore error. When I run roscore, the screenshot is presented as follows.


I only open a terminal, and thus I am sure I do not run another roscore. Besides, when I run roslaunch, it does not print an error, but all wait. I guess whether the ROS_MASTER_URT set is right or not. Thanks in advance and best regards. The error is further presented as bleow.

roscore cannot run as another roscore/master is already running. Please kill other roscore/master processes before relaunching. The ROS_MASTER_URI is http://yxg-Inspiron-5443:11311/ The traceback for the exception was written to the log file

 2 No.2 Revision gvdhoorn 76459 ●224 ●1118 ●935 http://cor.tudelft.nl/

### roscore error, ROS_MASTER_URI

Hello! Everyone. I have encountered an roscore error. When I run roscore, the screenshot is presented as follows.

follows.

I only open a terminal, and thus I am sure I do not run another roscore. Besides, when I run roslaunch, it does not print an error, but all wait. I guess whether the ROS_MASTER_URT set is right or not. Thanks in advance and best regards. The error is further presented as bleow.

roscore cannot run as another roscore/master is already running.
Please kill other roscore/master processes before relaunching.
The ROS_MASTER_URI is http://yxg-Inspiron-5443:11311/
The traceback for the exception was written to the log filefile