CentOS

I am still having a production running CentOS 6.5. right now every time when I boot up PC and it will pop up a screen showing: Problem connecting to a software source, There was (possibly temporary)problem connecting to a software source, please check the detailed error for further details.
Then I click to check detail and see: can not find a valid baseurl for repo extras

but I already disable yum update manager:
chmod -R 000 /etc/yum/ ;
chmod 000 /etc/yum.conf ;
chmod -R 000 /etc/yum.repos.d/ ;
chmod 000 /usr/bin/yum ;
chmod -R 000 /usr/share/yum-cli ;

Is there any other am I missing?
Thanks

Yes, you're missing two things:

1) CentOS 6.5 is from late 2013 and went out of support as soon as 6.6 was released in late 2014.
2) All of CentOS 6 went EOL completely at the end of Nov 2020 and its repos have been removed from all mirrors and moved to vault.centos.org

It's unsupported, get off it ASAP. The sudo bug from yesterday will never be fixed on CentOS 6 f.e.

Thank you for replying TreVorH.

This pop-up also happened when the machine unplug the network cable and running as a standalone PC. It confused me.