enable sudo in rhel

this is very useful and simple but some times I forgot.
login as root and type visudo

## The COMMANDS section may have other options added to it.
##
## Allow root to run any commands anywhere
root    ALL=(ALL)       ALL
sysadmin ALL=(ALL) NOPASSWD: ALL
oracle ALL=(ALL) NOPASSWD: ALL
grid ALL=(ALL) NOPASSWD: ALL