【已解决】roscore没反应或roscore cannot run as another roscore/master is already running

1 问题背景

环境：

• Ubuntu20.04
• ROS noetic

现象：

• roscore没反应
  
  
• roscore cannot run as another roscore/master is already running
  
  

2 问题探索

对于roscore没反应的问题，等待一段时间后出现信息

RLException: Unable to contact my own server at [http://192.168.31.249:46867/].
This usually means that the network is not configured properly.A common cause is that the machine cannot connect to itself.  Please check
for errors by running:ping 192.168.31.249For more tips, please seehttp://wiki.ros.org/ROS/NetworkSetupThe traceback for the exception was written to the log file

即运行ping 192.168.31.249时出错，这表明ROS系统分布式通信失败。而ROS初始化中涉及IP设置的是主从配置，可以参考 ROS从入门到精通8-1：多机器人控制(主从机配置)与launch递归启动，因此终端输入

sudo gedit ~/.bashrc

查找ROS IP配置

终端输入

ifconfig

查看实际IP，将ROS_IP修正为实际IP地址即可(或直接注释)

对于roscore cannot run as another roscore/master is already running这个问题，实际上是因为系统已经启动了一个ROS节点，杀掉保持唯一性即可

3 问题解决

• roscore没反应

  解决方案： 将~/.bashrc中的ROS_IP修正为实际IP地址即可

• roscore cannot run as another roscore/master is already running

  解决方案：杀掉已有的ros节点管理器

  killall -9 roscore && killall -9 rosmaster
  

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