There are several reasons why someone might want to enable root login on their Mac. From a security perspective, setting a root password is a way to “take ownership” of the super user account and effectively restricts the possibility for someone else to do so in your place. In some other cases, you may need to login as root for boot manipulation and other very low level operations.
In most cases, you don’t need to have root access enabled to execute commands as the super user. The following command works just as well most of the time:
$ sudo -s
When prompted, enter the password for your account. You need to be logged in as an Administrator to execute this command. This will not work if you are a Standard or Guest user.
Like in previous versions of Mac OS X, logging in as root is disabled by default. Luckily, enabling root access can be done in a few simple steps.