CentOS virt - Mar 2015 - CentOS 6 VM image for paravirtualizaton on CentOS Xen server

On Sun, Mar 15, 2015 at 3:17 PM, Pasi K?rkk?inen <pasik at iki.fi>
wrote:
> On Thu, Mar 12, 2015 at 10:34:39PM -0400, Nico Kadel-Garcia wrote:
>> I'm looking at a CentOS 5  Xen server that I'd really like to
put some
>> more recent VM's. There are reasons not to touch it at the moment,
so
>> I can't upgrade it in place today.
>>
>> Has anyone successfully installed a CentOS 6 VM, paravirtualized, on a
>> CentOS 5 Xen server , without significant Xen upgrades? If so, can I
>> get a copy from a reputable source, or one that I can review before
>> using? I'm having a bit of difficulty arranging a PXE enironment to
do
>> a paraviirtualized installation with, and there are apparently
>> difficulties doing a paravirtualzed system with CD or DVD installation
>> with Xen.
>>
>>                           Nico Kadel-Garcia <nkadel at gmail.com>
>
> Yep, CentOS 6 VMs run just fine on CentOS 5 Xen host.
I've got CentOS VM's running fine, and have done them before. But
previously, I deployed the same base OS on the VM as on the Xen
server, so paravirtualization posed few risks. And I had control of
the DHCP setup. so I could trivially set up a tftp server to do a
non-CD installation, because Xen, at last look, doesn't support
installing a paravirtualized host from a CD image.

So I'm right back to my effectively unanswered original questions. So
please: I asked a very specific pair of questions, and they remain
unanswered. CentOS 5 Xen server (hypervisor, or Dom0, whatever we want
to call it this week): Does CentOS 6 work, paravirtualized, on such a
server? And given my deployment issues, does anyone have a base OS
image I can get a copy of?

On 03/16/2015 11:25 AM, Nico Kadel-Garcia wrote:
> I've got CentOS VM's running fine, and have done them before. But
> previously, I deployed the same base OS on the VM as on the Xen
> server, so paravirtualization posed few risks. And I had control of
> the DHCP setup. so I could trivially set up a tftp server to do a
> non-CD installation, because Xen, at last look, doesn't support
> installing a paravirtualized host from a CD image.
It does as long as (1) the kernel has Xen PV support (CentOS 6 standard
kernel does) and (2) it has the necessary drivers in the initrd (I think
this is where the CD image is lacking), then you should, in theory, be
able to pv-grub boot to the CD.  Alternatively you can boot to the CD on
another box first, copy the kernel off to a USB stick, and generate a
new initrd with the xen drivers included, then put those on the Xen host
and boot to the VM CD image using those in the kernel= and initrd= lines
in the domain.cfg file.

The other way is to boot to the CD as an HVM domain and install, then
convert it to a PV domain afterwards, which is not all that difficult to do.

There is a third way which involves using yum to install the @core group
plus kernel to an image, then tweak and boot to that as a PV domain.
This is how I have done it in the past.
> So I'm right back to my effectively unanswered original questions. So
> please: I asked a very specific pair of questions, and they remain
> unanswered. CentOS 5 Xen server (hypervisor, or Dom0, whatever we want
> to call it this week): Does CentOS 6 work, paravirtualized, on such a
> server?
Yes, I have done that until I upgraded the CentOS 5 host to CentOS 6 a
couple years ago.
> And given my deployment issues, does anyone have a base OS
> image I can get a copy of?
Sorry my image templates that I use are highly customized for my own
work, but I have told you three different ways to accomplish it above.


Peter

On 03/15/2015 03:25 PM, Nico Kadel-Garcia wrote:
> So I'm right back to my effectively unanswered original questions. So
> please: I asked a very specific pair of questions, and they remain
> unanswered. CentOS 5 Xen server (hypervisor, or Dom0, whatever we want
> to call it this week): Does CentOS 6 work, paravirtualized, on such a
> server? And given my deployment issues, does anyone have a base OS
> image I can get a copy of?
I'm not sure why you need tftp to do a net install assuming you control the
guest configuration.

How about

kernel = file from
https://mirrors.kernel.org/centos/6/os/i386/images/pxeboot/vmlinuz
ramdisk = file from
https://mirrors.kernel.org/centos/6/os/i386/images/pxeboot/initrd.img
extra = "console=hvc0"
memory = 512 or larger

--Sarah

On Sun, Mar 15, 2015 at 8:26 PM, Sarah Newman <srn at prgmr.com>
wrote:
> On 03/15/2015 03:25 PM, Nico Kadel-Garcia wrote:
>> So I'm right back to my effectively unanswered original questions.
So
>> please: I asked a very specific pair of questions, and they remain
>> unanswered. CentOS 5 Xen server (hypervisor, or Dom0, whatever we want
>> to call it this week): Does CentOS 6 work, paravirtualized, on such a
>> server? And given my deployment issues, does anyone have a base OS
>> image I can get a copy of?
>
> I'm not sure why you need tftp to do a net install assuming you control
the guest configuration.
>
> How about
>
> kernel = file from
https://mirrors.kernel.org/centos/6/os/i386/images/pxeboot/vmlinuz
> ramdisk = file from
https://mirrors.kernel.org/centos/6/os/i386/images/pxeboot/initrd.img
> extra = "console=hvc0"
> memory = 512 or larger
>
> --Sarah
I'll be happy to try this. Thank you for the pointer. Are you
confident that 'console=hvc0' is the right installation time message
for this? And will I be able to access a CD or DVD image for actual OS
installation with these options?

I'd really prefer to work from 'virsh' than from hand-writing xl
configuration files.When I last did this sort of thing, I worked from
a PXE environment that I controlled and could reserve DHCP settings
based on MAC addresses, and tune PXE to boot from disk by default but
allow users to select a clean re-install of the operating system they
wanted.

On Sun, Mar 15, 2015 at 8:11 PM, Peter <peter at pajamian.dhs.org>
wrote:
> On 03/16/2015 11:25 AM, Nico Kadel-Garcia wrote:
>> I've got CentOS VM's running fine, and have done them before.
But
>> previously, I deployed the same base OS on the VM as on the Xen
>> server, so paravirtualization posed few risks. And I had control of
>> the DHCP setup. so I could trivially set up a tftp server to do a
>> non-CD installation, because Xen, at last look, doesn't support
>> installing a paravirtualized host from a CD image.
>
> It does as long as (1) the kernel has Xen PV support (CentOS 6 standard
> kernel does) and (2) it has the necessary drivers in the initrd (I think
> this is where the CD image is lacking), then you should, in theory, be
> able to pv-grub boot to the CD.  Alternatively you can boot to the CD on
Not according to the Xen guidelines I was finding. If they're
incorrect, *for a CentOS 5 Xen hypervisor*, I'd love to be able to use
that. Unfortunately, one of the banes of my technology existence is
when people say "that works great!" and "just look on
Google,!", and
the answer they vaguely remember does not actually include the
situation I desdcribed.
> another box first, copy the kernel off to a USB stick, and generate a
> new initrd with the xen drivers included, then put those on the Xen host
> and boot to the VM CD image using those in the kernel= and initrd= lines
> in the domain.cfg file.
Ouch. I've hand-modified CD and DVD images in the past, it's a pain
the neck, It's been compunded by the insistece that the  compressed
"vmlinuz" file is, itself, named "vmlinuz" instead of
"vmlinuz.gz",
which always struck me as fairly nutty.
> The other way is to boot to the CD as an HVM domain and install, then
> convert it to a PV domain afterwards, which is not all that difficult to
do.
This would probably be safest for me right now, since I have a
testable HVM instance of CentOS 6 to copy and work with. I'm not
finding any good guidelines for migrating from HVM to
paravirtualizaton for old Xen environments. Have you seen any, or done
this process? The notes I find often include extraneous and hopefully
unnecessary steps, such as http://support.citrix.com/article/CTX121875
saying. It's legible, but leaves out the kind of incompatibility
issues that I;ve been concerned about hopping from a Xen server on
CentOS 5.x to a CentOS 6.x guest.
> There is a third way which involves using yum to install the @core group
> plus kernel to an image, then tweak and boot to that as a PV domain.
> This is how I have done it in the past.
I'm sorry, but what? Are you building a chroot cage yourself, such as
using 'mock', or are you starting with someone else's working
para-virtualized image? (See my notes above).
>> So I'm right back to my effectively unanswered original questions.
So
>> please: I asked a very specific pair of questions, and they remain
>> unanswered. CentOS 5 Xen server (hypervisor, or Dom0, whatever we want
>> to call it this week): Does CentOS 6 work, paravirtualized, on such a
>> server?
>
> Yes, I have done that until I upgraded the CentOS 5 host to CentOS 6 a
> couple years ago.
Thanks! THAT is one of the questions I really wanted an answer for.
>> And given my deployment issues, does anyone have a base OS
>> image I can get a copy of?
>
> Sorry my image templates that I use are highly customized for my own
> work, but I have told you three different ways to accomplish it above.
Well, dang!