OnApp KVM to KVM with virtio

1. Preparation

1.1. Prepare OnApp’s DB

Get the VM’s TEMPLATE_ID:

SELECT template_id FROM virtual_machines WHERE identifier="$VM_IDENTIFIER";

Create a copy of a template entry $TEMPLATE_ID in the onapp database with virtio enabled and note it’s id ( later referenced as $COPY_TEMPLATE_ID)

CREATE TEMPORARY TABLE tmptemplates SELECT * FROM templates WHERE id="$TEMPLATE_ID";
ALTER TABLE tmptemplates DROP id;
UPDATE tmptemplates SET virtualization='xen,kvm,kvm_virtio';
INSERT INTO templates SELECT 0,tmptemplates.* FROM tmptemplates;
DROP TEMPORARY TABLE templatestmp;
SELECT LAST_INSERT_ID();

Note

A new template should be created for each template without kvm_virtio. The new template is not usable for instantiating new VMs or re-building the current ones. For that to work the template image should be updated to support virtio which is out of scope of this guide.

1.2. Alter the VM’s content

Note

Currently only CentOS 5.x is researched but it should be similar for other Linux distributions as well.

1.2.1. CentOS 5.x

Replace /dev/hd with /dev/vd in
- /boot/grub/menu.lst - the root= in the cmdline
- /etc/fstab - all disk mounts
Edit /etc/modprobe.conf - add/replace alias eth0 xvnet to alias eth0 virtio_blk
Rebuild /boot/initrd-$(uname -r).img

# backup the initrd image
cp -v /boot/initrd-$(uname -r){,kvm}.img
# create a new initrd image
mkinitrd -v -f --with=virtio_blk --with=virtio_net --with=virtio_balloon \
               --with=virtio_pci --builtin=xenblk \
               /boot/initrd-$(uname -r)virtio.img $(uname -r)
# replace the booting initrd image
cp -v -f /boot/initrd-$(uname -r){virtio,}.img

1.3. Update the VM’s metadata in the OnApp’s DB

Replace the VM’s template with the new one:

UPDATE virtual_machines SET template_id="$COPY_TEMPLATE_ID"
                        WHERE identifier="$VM_IDENTIFIER";

1.4. Finalize

Reboot the VM via the OnApp Control Panel.