learning to buildworld

[Jonathan Horne]

i have begun spending a good deal of time researching and practicing the
buildworld process on my dev boxes.  i want to make sure i have the entire
process down pat, before i attempt it on my production server.

the handbook states that i should:

make buildworld
make buildkernel
make installkernel

and then reboot to single usermode.  the installworld comes while in
single user mode, and my production server would see quite a bit of
downtime over this.  handbook says to, in sigle user mode:

mergemaster -p
make installworld
mergemaster
reboot

ive seen several articles on the net, and of course, no one agrees on the
exact steps to take to update your system.  my question is, is it safe to
'mergemaster' and 'make installworld' while still up and running?  or do i
just need to bite the downtime-bullet, and put it in single user?

my server is co-located, so its not exactly convenient to put it in single
user mode, so if there is any reason to believe the whole processes can be
completed safely without single-user mode, then i will probably try it.

thanks,
jonathan