[lug] Mac unix root account and /etc/hosts

[dio2002 at indra.com]

any mac users out there?

i'm trying to help somebody with a mac.  i need to change /etc/hosts.  i'm
able to use terminal to get to the shell.  i can't save changes to
/etc/hosts because i'm not root.  i've tried su but it wants a root
password.

the mac user doesn't know of any other 'admin' account other than the user
they login as.  fwiw, as a test i tried to accomplish the same task with a
more savvy mac user friend who's got a laptop. he had no idea that there
is another account other than the user id he normally logs in as.

so the question is / are.

what is the mac account that gets you root access?
how do you access it or activate it if it's not enabled?
how do you reset the password if noone knows what it is?

hopefully some mac unix gurus out there.  my online searches have proved
fruitless for what seems like a fairly common question / problem.