Collins, Kevin [MindWorks] wrote:
Hi,
can anyone tell me how to determine (in Xen) whether a guest
OS was installed as paravirtual vs. fully virtual? Is that something
that can be changed without a re-install assuming the OS, RHEL5 in
this case, supports it? I've looked in the config files for the
various systems and I can't tell...
Thanks,
Keivn
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Hi,
one of the easier options to figure out if you are running in a
para-virt vs fully-virt/HVM guest
is to use either check the kernel name and/or the output "dmidecode"
(there are other examples
as well but lets keep it easy first :) ) .
At least in RHEL/Fedora the kernel used in dom0 and a para-virt
guest has always
the extension 'xen' (ie RHEL5 GA is 2.6.18-8.el5xen) , the kernel in
a fully-virt/HVM
guest will have the same name as the bare metal kernel (ie
2.6.18-8.el5 for RHEL5 GA if
it is running as a fully-virt guest).
In a HVM/fully-virt guest you could also use dmidecode and check the
Vendor/Product
fields which should come up as "Xen" (Vendor) and "HVM domU" (Product) .
You can find a simple script at
http://et.redhat.com/~jmh/virt-tools/scripts/ called
xen-type.sh which can be used to figure out in which type guest
and/or bare metal
you are running .
If you want to conver a fully-virt guest into a para-virt guest
you'd have to
install the para-virt kernel for the OS , make sure the entry for
the para-virt
kernel is the default boot target in your guest's /etc/grub.conf and
edit /etc/modprobe.conf to
add the following lines to it
alias eth0 xennet
alias scsi_hostadapter xenblk
you also want to remove the lines referencing to eth0 and the
physical ethernet
card and the scsi_hostadapter if present and change it to point to
xenblk
The next step would be to edit the guest config file on your
dom0/HyperVisor
of the HVM guest and change the entries for vif, disk and remove the
entry "type=ioemu" from them.
You also may want to change the 'disk' entry and change
file:/PathToYourGuestImage
to tap:aio:/PathToYourGuestImage and the device name from hda (hvm)
to xvda (pv)
Next you want to uncomment/remove the entries for "builder" ,
"kernel" and "device_model"
Now add a line for "bootloader="/usr/bin/pygrub"
This should be it and you should be able to boot your guest again .
Now you can configure the network inside the guest and you should be
ready to go .
I am not sure if it's documented in my notes on RHEL5/Virt at
http://et.redhat.com/~jmh/docs/Installing_RHEL5_Virt.pdf but I will
add a section to the document if it's not already included .
Hth,
Jan
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