10.6.2 won't install to another volume other than the boot volume

Question

Report a possible bug to Apple.
as is often recommended for updates, I install from another volume other than the one I want to update, and never update the volume I am booted from. The 10.6.2 update (both combo and update only) won't update any other volume other than the one booted from. Previous updates of OS X have always been able to do this. When I try to change installation location to another volume (which contain 10.6.1) it posts an error saying "This update requires 10.6.2 to be installed", which is wrong it two ways. First, how can an upgrade require itself to be installed before it will actually install. Second, there is no reason it shouldn't have been able to update the 10.6.1 volume. I had two 10.6.1 volumes, when booting from either one, it wouldn't update the other. The update will install if it's run on the volume I boot from, but that defeats the purpose of trying to eliminate update issues by installing from another volume.

Answer 1

-update-
In order to to update remotely, there seems to be a number of new and interesting restrictions
imposed. I came to these basic conclusions by experimentation:
1. I was unable to install a 10.6.2 update to a remote 10.6.0/10.6.1 volume, while booted from
a 10.6.0/10.6.1 volume. In other words I had to be booted from a 10.6.2 volume to be able to
remotely install (or reinstall) a 10.6.2 update to a remote 10.6.0/1/2 volume.
2. If the volume I was installing to was another internal volume, then I usually (but not
always) had to set the volume I was trying to install to, as the default startup volume in system
preferences before the installer would accept it as a valid volume to update.
3. If the volume I was installing to was a firewire or USB drive, then the #2 restriction did not apply,
but the the #1 restriction still applied (I still had to be booted from a 10.6.2 volume to install
a 10.6.2 update).
4. If, after following the above rules, you are still having trouble, simply rebooting and trying
again will usually work.
So in conclusion:
Remotely updating an external firewire or USB drive was relatively simple and easy, just boot
from an internal 10.6.2 installation and do it.
Remotely updating another internal drive though, can be quite annoying.
Apple, it seems, is heavily promoting the automatic update method.
Lately, it seems, it is getting more and more difficult in many cases, to get a major
OS update to "take" properly. I have been heavily using the "bare bones admin account"
method (outlined in my previous post) for the last several months with good success.
I agree with you that the remote method should be the best, but Apple's install packages
have become increasingly difficult to install using that method, even in 10.5.x.
I will say this though, the updates I installed today using the remote method
are working just fine, even though I had to wrestle with them to get them installed.
Kj ♘