[CentOS] Crazy idea for a portable CentOS installation

Sat May 19 17:53:40 UTC 2007
Bart Schaefer <barton.schaefer at gmail.com>

I've got CentOS up and running on my hp pavilion laptop.  There wasn't
enough space on the internal hard drive to shrink the NTFS partition
and install CentOS there, and I didn't want to go through the exercise
of copying everything to a new larger internal drive until I knew 5
was going to work, so it's installed on an external USB drive --
except for /boot which had to be on the internal drive in order for
grub to properly dual-boot XP and CentOS.

Now the thought occurs to me:  Is there some way I can easily carry
this external drive to another machine, plug it in, and boot up the
same CentOS installation?  There are two constraints: (1) There is no
/boot on this drive, so I have to re-create that, and (2) I don't want
to have the /etc configuration that works with my laptop destroyed by
whatever kudzu finds on any other machine I might plug in to, so I
need a separate /etc.

Which leads to my question:  Can I somehow:
* copy /boot and /etc onto separate partitions on either this USB
drive or a thumb drive [let's say a thumb drive for clarity in the
rest of this paragraph], and
* re-run grub to install a boot loader on the thumb drive, such that
* the end result is that when I boot the laptop from the internal disk
with the CentOS USB plugged in, I get exactly what I have now, but
* when I boot from the thumb I get the root from the CentOS USB with
the thumb /boot and /etc mounted over it?

Kudzu could thus do whatever it needs to for the current hardware in
the thumb /etc, without changing the original /etc, but everything
else would be exactly as it is when I boot the laptop.

Is there any chance at all this will work?  I assume to change the
boot device and reassign the /boot and /etc mount points I'll have to
boot from the rescue CD.  I've never done a grub reinstall by hand
before (always used lilo in the past) so I'd appreciate pointers to
the specifics of doing that for CentOS 5.