In pretty much any GNU/Linux distribution you use
su, What's the right choice for FreeBSD 10 ?
FreeBSD does support
sudo it's likely just not installed by default. Installation instructions are here, titled: FreeBSD: Install sudo Command To Execute A Command As The Root.
FreeBSD < 10
# pkg_add -r sudo
# pkg install sudo
sudoers file is located here:
/usr/local/etc/sudoers. To edit it and add rules you need to use the
$ su - $ visudo
Then to give a user access to everything as root:
userX ALL=(ALL) ALL
To become root (as userX):
$ sudo -s -or- $ sudo -i