List which repos are enabled

yum repolist


Disable repos

yum-config-manager --disable <repository>


Add a repo

yum-config-manager --add-repo <http://www.example.com/example.repo>


Enable repos

yum-config-manager --enable <repository>


Search for packages:

yum search <keyword>


Install Package:

yum install <packageName>


Show available package groups

yum grouplist


Install package group:

yum groupinstall "<package group name>"


Search package that provides or as keyword in name:

yum provides <keyword>


Get info on a package

yum info <packageName>


List packages that can be updated

yum list updates


Check for available updates

yum check-update


Update system:

yum update


Remove rpm packages in /var/cache/yum and heads of packages that are no longer in the database

yum clean all


Rollback 

yum history
yum history undo <id>  or yum history rollback <id>


View history of a package

yum history list <packageName>
yum history package-list <packageName>


Show packages available from only one rep

yum --disablerepo="*" --enablerepo="google" list available