Suggestions for upgrading dom0

[Jeff Rizzo <riz%tastylime.net@localhost>]

Benign neglect has left me in a situation where I have a dom0 at a 
remote site which is in need of an upgrade, but being on-site for it is 
a lot of trouble, and I'm willing to take some risk of everything 
blowing up in order to do it remotely.  That said, I'd like to minimize 
my risk to the extent possible, and I was hoping to get some suggestions 
from others.


The dom0 in question is running NetBSD 6.1.2/amd64, and Xen 4.1.6, and 
it's been up for 1062 days(!).  The domUs are mostly PV, with one HVM, 
all running versions of NetBSD from 5.1 to 7. (In fact, the thing that's 
getting me to finally bite the bullet is that I can't get a NetBSD 8 PV 
kernel to run).  The domUs are backed by LVM volumes.  Xen is installed 
via pkgsrc.


What I'm *hoping* I can do is upgrade to NetBSD-8.0 and whatever the 
latest Xen in pkgsrc is (looks like 4.11.x maybe?) with something 
approximating this:


First, my standard NetBSD upgrade:

- install new netbsd kernel and kernel modules in a new line of 
/boot.cfg , shut down all domUs, and reboot. (Unclear whether I can get 
the xen4.1.6 kernel working with the new dom0 kernel; I'll probably have 
to fiddle to get things booted with a xen 4.11.x kernel as well)

- unpack NetBSD8 sets, do the etcupdate dance. and reboot again

- using pkgin, upgrade all packages to NetBSD-8 packages. Install 
xentools411 and xenkernel411, put the kernel in the proper location, and 
reboot again.

- get the new xend rc.d script (and any others needed) working

- figure out how to get each domU booted using xl instead of xm

- get the xendomains rc.d script working

- reboot one more time to make sure all domUs come up at boot.


Having attempted this sort of thing before, I'm expecting I'll hit a 
snag at one or more places.  I'm a little worried about this being a 
one-way trip; once I overwrite the 6.1.2 OS binaries with 8.0, I won't 
be able to roll back.  Any suggestions for success are greatly 
appreciated.  I'm particularly concerned with:


- whether xend from xen 4.11 is likely to give me trouble

- whether I'll need to update any scripts.  I'm pretty sure the 
pkgsrc-provided xen scripts are stock (that is, I didn't patch them locally)

- what I should be looking at that I haven't.

The last time I did anything fancy with a dom0 (specifically, getting 
this one set up) would have been just before NetBSD 6 was released, so 
anything that's changed in the Xen world since then is likely to 
surprise me.  I kind-of recall that xm has been replaced by xl, but I'm 
not yet sure of the ramifications of that.

Suggestions gratefully accepted.

+j