"ROS_DISTRO was set to 'noetic' before" while sourcing ROS 2 setup.bash

edit

Is it correct or i should do any configurations? please tell me thanks in advance

future_engineer@grayhat:~$ source /opt/ros/galactic/setup.bash
ROS_DISTRO was set to 'noetic' before. Please make sure that the environment does not mix paths from different distributions.
future_engineer@grayhat:~$ env |grep ROS
ROS_VERSION=2
ROS_PYTHON_VERSION=3
ROS_PACKAGE_PATH=/opt/ros/noetic/share
ROSLISP_PACKAGE_DIRECTORIES=
ROS_ETC_DIR=/opt/ros/noetic/etc/ros
ROS_MASTER_URI=http://localhost:11311
ROS_LOCALHOST_ONLY=0
ROS_ROOT=/opt/ros/noetic/share/ros
ROS_DISTRO=galactic