This error message indicates that there is another instance of the yum package manager currently running on the system. Yum is designed to prevent multiple instances from running simultaneously in order to prevent conflicts and ensure the integrity of the package database.
To resolve this issue, you can wait for the other instance of yum to complete its operation and release the lock on the yum.pid file, or you can manually remove the lock file if you are sure that there is no other instance of yum currently running.
To manually remove the yum.pid file, you can run the following command as the root user:
rm -f /var/run/yum.pid
This will delete the lock file and allow you to run yum again. However, be careful when deleting lock files as it can lead to inconsistent states or package database corruption.