Hi Paul,
On Tue, Jan 04, 2022 at 02:28:07PM +0000, Paul Tansom wrote:
> You say that's no problem for Ubuntu as there's been no support
> for some time, but I'm running Ubuntu 18.04, i686 in PV mode.
Yeah :) I meant more that upgrading hasn't been an issue since there
never has been an upgrade path for 32-bit Ubuntu 18.04.
It's more a question of assumptions. We've had a bunch of customers
on Debian assume that upgrades will just work, and a 32-bit buster
to bullseye upgrade in PV mode DOES appear to work, until they
reboot! So it's a case of it being an unexpected problem and scary
if you don't know that you just have to switch to PVH mode.
> I'm reading up with a plan to either switch over manually (trying
> to get my head around the instructions and fallback options if it
> goes wrong)
The simplest thing you can do is try out the pvshim by doing this:
xen shell> arch i686
(even though you are already on i686)
That will implement the config change to change you to pvshim, the
same change that is going to happen for all the remaining 32-bit PV
guests on 18 January.
I have not yet seen this fail to work, but trying it ahead of time
is still a good idea as it will take effect from your next boot so
best to be prepared for it as opposed to it happening just whenever
you next have need to reboot. So then:
xen shell> shutdown
xen shell> boot
If you are already on a kernel newer than 4.19.0 and running grub2
(boots with /boot/grub/grub.cfg) then the next easiest thing would
be instead to switch to PVH mode.
xen shell> virtmode pvh
xen shell> shutdown
xen shell> boot
The *best* thing would be 64-bit PVH mode, but that is either some
hassle installing a 64-bit kernel, lots more hassle doing a full
cross-grade, or some work setting up a whole new VM.
> So, some quick questions:
>
> - has Ubuntu 18.04 i686 been tested under PVH?
Yes and it does not work because Ubuntu 18.04 comes with a 4.15.x
kernel:
https://tools.bitfolk.com/wiki/PVH#Ubuntu
If you can get onto a newer kernel such as by installing the
linux-generic-hwe-18.04 package or one of the other various packaged
newer kernels then it should work; we've had only successful reports
from customers doing this.
You then would get to live out the remaining support life of 18.04
(bearing in mind that only a subset of the packages in "main" do
have support).
> - a previous email talked about needing support if the switch on
> an existing 32bit goes wrong, but the PVH web page talks about
> switching back; am I right in thinking that you can switch back
> and then get support or is the support to get your VPS working
> again?
The issue now is that we no longer support 32-bit PV mode guests so
there is purposefully no way to switch back to that. When you select
32-bit PV it will actually do pvshim; the only other option is
32-bit PVH.
Those still running as 32-bit PV are in a transitional state now
that will be resolved in 2 weeks by being forcibly moved to pvshim.
As I say, we haven't yet encountered a failure on switching to
pvshim, but not every combination has been tested so we can't
definitively say it will work. If you want us to do the switch for
you then that's fine, just drop an email to support@???
asking for that and saying when to do it. The advantage being that
we will be able to quickly roll the change back should there be a
problem.
> Switching to 64bit is my plan, with 32bit PVH as a temporary fall
> back, so just trying to get my ducks in a row first.
When you say "switching to 64bit", do you mean by means of a new
account that you will migrate your stuff into? I ask because I
wouldn't necessarily recommend the other options.
Just installing to a 64-bit kernel is easy but given there is no
upgrade path for the 32-bit userland with Ubuntu, so it's not a good
long term plan.
That leaves a full cross-grade to 64-bit which I would say is more
work than migrating and things are broken while you do it.
Hopefully that explains the situation and your options but if
there's anything else that's unclear please do let us know!
Cheers,
Andy
--
https://bitfolk.com/ -- No-nonsense VPS hosting
