= Guest migration between hosts.

Move guests from one host to another.

== Contact Information

Owner::
  Fedora Infrastructure Team
Contact::
  #fedora-admin, sysadmin-main
Location::
  IAD2, Tummy, ibiblio, Telia, OSUOSL
Servers::
  All xen servers, kvm/libvirt servers.
Purpose::
  Migrate guests

== How to do it

[arabic]
. Schedule outage time if any. This will need to be long enough to copy
the data from one host to another, so will depend on guest disk size.
. Turn off monitoring in nagios
. On new host create disk space for server:
+
....
lvcreate -n app03 -L 32G vg_guests
....
. prepare old guest for migration:
[loweralpha]
.. if system is xen, install a regular kernel
.. look for entries for xenblk and hvc0 in /etc files
. Shutdown the guest.
. {blank}
+
....
virsh dumpxml guestname > guest.xml
....
. Copy guest.xml to the new machine. You will need to make various edits
depending on if the system was originally xen or such. I normally need
to compare an existing xml on the target system and the one we dumped
out to make up the differences.
. Define the guest on the new machine:

....
virsh define guest.xml
....

Depending on the changes in the xml this may not work and you will need
to make many manual changes plus copy the guest.xml to
`/etc/libvirtd/qemu` and do a `/sbin/service libvirtd restart`

. Insert iptables rule for nc transfer:
+
....
iptables -I INPUT -s <source host> -m tcp -p tcp --dport 11111 -j ACCEPT
....
. On the destination host:
+
____
nc -l 11111 | dd of=/dev/mapper/<guest-partition>
____
. On the source host:
+
....
dd if=/dev/mapper/guest-partition | nc <desthost> 11111
....
+
Wait for the copy to finish. You can do the following to track how far
something has gone by finding the dd pid and then sending a 'kill -USR1'
to it.
. start the guest on the new host:
+
....
``virsh start guest``
....

. To ensure that the new vm starts automatically after boot run:

....
virsh autostart guest
....

. On the source host, rename storage and undefine guest so it's not
started.
. In ansible change the host_vars to reflect the new host
