Installation guide
Note that the address used for migration data cannot be automatically determined from the
address used for connecting to destination lib virt d (for example, from
q emu+ tcp: //19 2. 16 8. 122. 12/system). This is because to communicate with the
destination lib virt d , the source lib virt d may need to use network infrastructure different
from that which virsh (possibly running on a separate machine) requires.
So lu t io n
The best solution is to configure DNS correctly so that all hosts involved in migration are
able to resolve all host names.
If DNS cannot be configured to do this, a list of every host used for migration can be added
manually to the /etc/ho sts file on each of the hosts. However, it is difficult to keep such
lists consistent in a dynamic environment.
If the host names cannot be made resolvable by any means, vi rsh mi g rate supports
specifying the migration host:
# virsh migrate qemu qemu+tcp://192.168.122.12/system
tcp://192.168.122.12
Destination lib virt d will take the tcp: //19 2. 16 8. 122. 12 URI and append an
automatically generated port number. If this is not desirable (because of firewall
configuration, for example), the port number can be specified in this command:
# virsh migrate qemu qemu+tcp://192.168.122.12/system
tcp://192.168.122.12:12345
Another option is to use tunnelled migration. Tunnelled migration does not create a
separate connection for migration data, but instead tunnels the data through the
connection used for communication with destination lib virt d (for example,
q emu+ tcp: //19 2. 16 8. 122. 12/system):
# virsh migrate qemu qemu+tcp://192.168.122.12/system --p2p --
tunnelled
B.14 . Migrat ion fails wit h Unabl e to al l o w access fo r d i sk path: No such
fi le o r d i recto ry
Symp t o m
A guest virtual machine (or domain) cannot be migrated because lib virt cannot access the
disk image(s):
# virsh migrate qemu qemu+tcp://name_of_host/system
error: Unable to allow access for disk path
/var/lib/libvirt/images/qemu.img: No such file or directory
For example, if the destination hostname is "newyork", the error message will appear as:
# virsh migrate qemu qemu+tcp://newyork/system
error: Unable to allow access for disk path
/var/lib/libvirt/images/qemu.img: No such file or directory
Red Hat Ent erp rise Linux 6 Virt ualiz at ion Host Configurat ion and G uest Inst allat ion G uide
14 6