已经解决了，python中PYTHONPATH变量需要设置一下。
在开发板上运行roscore之前，还需要运行 source /opt/ros/noetic/setup.bash，否则会提示找不到roslaunch
3116868751 发布的最新帖子
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RE: Debain10系统开发板下载ros1 noeteic(基础版)，运行roscore，报错。情况：默认python是3.7；已经把ros添加到了系统环境变量中；在/opt/ros/noetic/bin路径下存在rosmaster发布在 综合问题
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Debain10系统开发板下载ros1 noeteic(基础版)，运行roscore，报错。情况：默认python是3.7；已经把ros添加到了系统环境变量中；在/opt/ros/noetic/bin路径下存在rosmaster发布在 综合问题
root@ATK-DLRK3568-Debian:~#$PATH
-bash: /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/opt/ros/noetic/bin:/usr/bin/python3.7:/usr/bin/python3.7m:/opt/ros/noetic/bin/rosmaster: 没有那个文件或目录
root@ATK-DLRK3568-Debian:~# $PYTHONPATH
root@ATK-DLRK3568-Debian:~# roscore
Traceback (most recent call last):
File "/opt/ros/noetic/bin/roscore", line 36, in <module>
from rosmaster.master_api import NUM_WORKERS
ModuleNotFoundError: No module named 'rosmaster'
root@ATK-DLRK3568-Debian:~# cd /opt/ros/noetic/bin
root@ATK-DLRK3568-Debian:/opt/ros/noetic/bin# ls
catkin_find rosclean roslaunch-logs rosrun
catkin_init_workspace rosconsole rosmake rosservice
catkin_make roscore rosmaster rossrv
catkin_make_isolated roscreate-pkg rosmsg rosstack
catkin_test_results rosgraph rosmsg-proto rostest
catkin_topological_order roslaunch rosnode rostopic
rosbag roslaunch-complete rospack rosunit
rosboost-cfg roslaunch-deps rosparam roswtf