[Linux Tip] downgrade or undo yum/package install in RHEL 6

 downgrade or undo yum/package install in RHEL 6 is fairly straight forward

# yum history
ID | Login user | Date and time | Action(s) | Altered
-------------------------------------------------------------------------------
1 | root | 2014-04-07 21:21 | Downgrade | 3

now if you do

# yum -y history undo 1

it reverts your changes made in 1. sommetime, you have to run it with --skip-broken if it cannot resolve a dependency and run it couple of times to make sure the packages requested get removed.

Much more efficient than Red Hat's Recommended method to downgrade  OS versions