openstack/nova
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bfeea18358
nova/doc/source/admin/evacuate.rst
Matt Riedemann de32a70844 doc: mention that --on-shared-storage is not needed with nova evacuate 
The 2.14 microversion makes the --on-shared-storage calculation
happen automatically in the compute service, so we should make a note
of that in the evacuate CLI docs.

Change-Id: I88806897a2412971b3c7488155f17156ae1c7bf9
2018-02-08 19:43:39 -05:00

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Evacuate instances

If a hardware malfunction or other error causes a cloud compute node to fail, you can evacuate instances to make them available again. You can optionally include the target host on the nova evacuate command. If you omit the host, the scheduler chooses the target host.

To preserve user data on the server disk, configure shared storage on the target host. When you evacuate the instance, Compute detects whether shared storage is available on the target host. Also, you must validate that the current VM host is not operational. Otherwise, the evacuation fails.

  1. To find a host for the evacuated instance, list all hosts:

    $ openstack host list

  2. Evacuate the instance. You can use the --password PWD option to pass the instance password to the command. If you do not specify a password, the command generates and prints one after it finishes successfully. The following command evacuates a server from a failed host to HOST_B.

    $ nova evacuate EVACUATED_SERVER_NAME HOST_B

    The command rebuilds the instance from the original image or volume and returns a password. The command preserves the original configuration, which includes the instance ID, name, uid, IP address, and so on.

    +-----------+--------------+
| Property  |    Value     |
+-----------+--------------+
| adminPass | kRAJpErnT4xZ |
+-----------+--------------+

  3. To preserve the user disk data on the evacuated server, deploy Compute with a shared file system. To configure your system, see section_configuring-compute-migrations. The following example does not change the password.

    $ nova evacuate EVACUATED_SERVER_NAME HOST_B --on-shared-storage

    Note

    Starting with the 2.14 compute API version, one no longer needs to specify --on-shared-storage even if the server is on a compute host which is using shared storage. The compute service will automatically detect if it is running on shared storage.