Red Hat LINUX VIRTUAL SERVER 5.1 - ADMINISTRATION Guide d'installation télécharger pdf (Page 150)

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

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Red Hat LINUX VIRTUAL SERVER 5.1 - ADMINISTRATION Guide d'installation Page 150