I have tried that but getting the following error:
ptopping@tonic
[/home/ptopping]$ sudo yum clean metadata
Loading "kernel-module" plugin
Loading "fastestmirror" plugin
Existing lock /var/run/yum.pid: another copy is running as pid 12657.
Another app is currently holding the yum lock; waiting for it to exit...
Another app is currently holding the yum lock; waiting for it to exit...
I have checked /var/run and there isn't a file yum.pid: