In this chapter, I took you on an extensive tour of the Mac OS X accounts in their many facets. I explained how accounts work and what they have to do with security. Because permissions interact with accounts in such a crucial way, I described POSIX permissions at some length. I then explained the several varieties of user accounts you can create in Mac OS X and discussed how to configure each one, including managing an account with parental controls and setting overall login options. I explained how an administrator can temporarily gain root access by using the sudo command. And I rounded out the discussion on accounts with an overview of ACLs, which provide much more control than POSIX permissions.