upgrading from 4.2 to 4.10

[Zachary Huang]

So my system seems to be messed up (see previous messages).  I tried
cvsup to the old system 4.2 and it did not fix the problem.  Today I
tried "upgrading" using my old 4.2 CD (sysinstall again) but still get
many sendmail error messages (but seems to be sending and receiving
mails file).

1). what is the best way to fix this? I plan to buy the 4.10 Release
CDs, but then what? I boot the system with CD and do upgrade, but
/usr/src will not be changed. is it safe to remove /usr/src first?

2). I do not quite understand if one need to boot into the new system
(4.10) or not, after cvsup to a new source (say 4.10), before doing
the make buildworld. The book does not say so , so I assume not.

3). the FreeBSD book says I need to make sure all the ports are up to
date before installing JAVA but when I got the ports from 4.10 on a
4.8 system (a differen machine), I had trouble installing Linux
Runtime Lib.  So I am confused when the book says up to date, does it
mean to the same release? (i.e. I should have got ports from 4.8 since
my system is 4.8).

Thanks, 

Zach