Guest migration between hosts.

Move guests from one host to another.

Contact Information


Fedora Infrastructure Team


#fedora-admin, sysadmin-main


IAD2, Tummy, ibiblio, Telia, OSUOSL


All xen servers, kvm/libvirt servers.


Migrate guests

How to do it

  1. 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.

  2. Turn off monitoring in nagios

  3. On new host create disk space for server:

    lvcreate -n app03 -L 32G vg_guests
  4. prepare old guest for migration:

    1. if system is xen, install a regular kernel

    2. look for entries for xenblk and hvc0 in /etc files

  5. Shutdown the guest.

  6. virsh dumpxml guestname > guest.xml
  7. 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.

  8. 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

  1. Insert iptables rule for nc transfer:

    iptables -I INPUT -s <source host> -m tcp -p tcp --dport 11111 -j ACCEPT
  2. On the destination host:

    nc -l 11111 | dd of=/dev/mapper/<guest-partition>

  3. 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.

  4. start the guest on the new host:

    ``virsh start guest``
  5. To ensure that the new vm starts automatically after boot run:

virsh autostart guest
  1. On the source host, rename storage and undefine guest so it’s not started.

  2. In ansible change the host_vars to reflect the new host