The error message "existing lock /var/run/yum.pid: another copy is running as pid 523" typically indicates that another instance of the yum package manager is already running on your system and has a lock on the /var/run/yum.pid file. As a result, you are unable to run yum until the other instance finishes or the lock is removed.
To resolve this issue, you can try the following steps:
Check for other instances of yum: Use the ps command to list all running processes and see if there are any other instances of yum running. If you find any, you can try killing them using the kill command.
Check the lock file: Make sure that the /var/run/yum.pid file exists and contains the process ID of the running yum instance. If the file does not exist or is empty, you can try deleting it.
Restart the yum-updatesd service: The yum-updatesd service is responsible for checking for updates and installing them automatically. If this service is running, it may be holding the lock on the /var/run/yum.pid file. You can try restarting the service by running the following command:
sudo systemctl restart yum-updatesd
If none of these steps help, you may need to seek assistance from a qualified technician or consult the documentation for your Linux distribution for more information.