how do people play with different versions of DBSD on the same system?

[walt]

Bill Hacker wrote:
Bob Bagwill wrote:

How are people playing with different versions of DBSD on the same 
system?
[...]

- partition and slice your media into many (preferably equal sized) 
portions...
I like to point out at every opportunity that DragonFlyBSD is the
*only* BSD which can load the kernel from an extended DOS partition,
e.g. /dev/ad0s5a.  (This is because of our local modifications to
/boot/loader which (so far) have eluded the other BSD's.)
I don't know if the DFly installer will permit installation to an
extended partition/slice, however, because I haven't tried it.
The way I installed DFly to an extended partition is by doing a
byte-for-byte copy of my original DFly installation (using Acronis
Partition Expert, but I think Partition Magic might also do the job)
to an extended slice.  Remember that /etc/fstab will need to be
modified before booting the new copy of DFly.
I load and start /boot/loader by using GRUB, which is trivial.  I
have never used the *bsd master boot loader to choose which OS to
boot, so this may be a problem for people who don't use GRUB.
(I don't really know.)
Just as an off-topic aside -- I copied the /boot/loader executable
to my FreeBSD installation (in an extended DOS partition) and I
use it to boot FreeBSD as well.  I'm quite sure the FreeBSD install
program forbids using an extended slice for FreeBSD -- I also used
Partition Expert to copy my original install of FBSD to an extended
slice.
The whole thing is just trivial if you know what to look out for.
The main obstacle to using extended slices has been resistance from
developers who dismiss multi-booters as contemptible amateurs and
dilettantes.  (I plead guilty on both counts  ;o)
(I believe there are ways of byte-copying one partition to another
without using third-party applications.  (dd?)  If anyone knows
for sure how to do it using standard *nix tools, please tell me.)