285 lines
8.2 KiB
ReStructuredText
285 lines
8.2 KiB
ReStructuredText
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:orphan:
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.. _support-compute:
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====================
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Troubleshoot Compute
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====================
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Common problems for Compute typically involve misconfigured
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networking or credentials that are not sourced properly in the
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environment. Also, most flat networking configurations do not
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enable :command:`ping` or :command:`ssh` from a compute node
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to the instances that run on that node. Another common problem
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is trying to run 32-bit images on a 64-bit compute node.
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This section shows you how to troubleshoot Compute.
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.. _log-files-for-openstack-compute:
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Compute service logging
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~~~~~~~~~~~~~~~~~~~~~~~
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Compute stores a log file for each service in
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``/var/log/nova``. For example, ``nova-compute.log``
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is the log for the ``nova-compute`` service. You can set the
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following options to format log strings for the ``nova.log``
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module in the ``nova.conf`` file:
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* ``logging_context_format_string``
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* ``logging_default_format_string``
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If the log level is set to ``debug``, you can also specify
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``logging_debug_format_suffix`` to append extra formatting.
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For information about what variables are available for the
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formatter see http://docs.python.org/library/logging.html#formatter-objects.
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You have two logging options for OpenStack Compute based on
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configuration settings. In ``nova.conf``, include the
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``logfile`` option to enable logging. Alternatively you can set
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``use_syslog = 1`` so that the nova daemon logs to syslog.
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.. _section_compute-GuruMed-reports:
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Guru Meditation reports
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~~~~~~~~~~~~~~~~~~~~~~~
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A Guru Meditation report is sent by the Compute service upon receipt of the
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``SIGUSR2`` signal (``SIGUSR1`` before Mitaka). This report is a
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general-purpose error report that includes details about the current state
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of the service. The error report is sent to ``stderr``.
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For example, if you redirect error output to ``nova-api-err.log``
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using :command:`nova-api 2>/var/log/nova/nova-api-err.log`,
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resulting in the process ID 8675, you can then run:
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.. code-block:: console
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# kill -USR2 8675
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This command triggers the Guru Meditation report to be printed to
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``/var/log/nova/nova-api-err.log``.
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The report has the following sections:
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* Package: Displays information about the package to which the process
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belongs, including version information.
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* Threads: Displays stack traces and thread IDs for each of the threads
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within the process.
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* Green Threads: Displays stack traces for each of the green threads
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within the process (green threads do not have thread IDs).
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* Configuration: Lists all configuration options currently accessible
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through the CONF object for the current process.
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For more information, see `Guru Meditation Reports <http://docs.openstack.org/developer/nova/devref/gmr.html>`_.
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.. _compute-common-errors-and-fixes:
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Common errors and fixes for Compute
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The `ask.openstack.org <http://ask.openstack.org>`_ site offers a place to ask
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and answer questions, and you can also mark questions as frequently asked
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questions. This section describes some errors people have posted previously.
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Bugs are constantly being fixed, so online resources are a great way to get
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the most up-to-date errors and fixes.
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Credential errors, 401, and 403 forbidden errors
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Problem
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-------
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Missing credentials cause a ``403 forbidden`` error.
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Solution
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--------
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To resolve this issue, use one of these methods:
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#. Manual method
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Gets the ``novarc`` file from the project ZIP file, saves existing
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credentials in case of override, and manually sources the ``novarc``
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file.
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#. Script method
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Generates ``novarc`` from the project ZIP file and sources it for you.
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When you run ``nova-api`` the first time, it generates the certificate
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authority information, including ``openssl.cnf``. If you
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start the CA services before this, you might not be
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able to create your ZIP file. Restart the services.
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When your CA information is available, create your ZIP file.
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Also, check your HTTP proxy settings to see whether they cause problems with
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``novarc`` creation.
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Instance errors
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~~~~~~~~~~~~~~~
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Problem
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-------
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Sometimes a particular instance shows ``pending`` or you cannot SSH to
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it. Sometimes the image itself is the problem. For example, when you
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use flat manager networking, you do not have a DHCP server and certain
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images do not support interface injection; you cannot connect to
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them.
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Solution
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--------
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To fix instance errors use an image that does support
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this method, such as Ubuntu, which obtains an IP address correctly
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with FlatManager network settings.
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To troubleshoot other possible problems with an instance, such as
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an instance that stays in a spawning state, check the directory for
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the particular instance under ``/var/lib/nova/instances`` on
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the ``nova-compute`` host and make sure that these files are present:
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* ``libvirt.xml``
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* ``disk``
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* ``disk-raw``
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* ``kernel``
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* ``ramdisk``
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* ``console.log``, after the instance starts.
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If any files are missing, empty, or very small, the ``nova-compute``
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service did not successfully download the images from the Image service.
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Also check ``nova-compute.log`` for exceptions. Sometimes they do not
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appear in the console output.
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Next, check the log file for the instance in the ``/var/log/libvirt/qemu``
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directory to see if it exists and has any useful error messages in it.
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Finally, from the ``/var/lib/nova/instances`` directory for the instance,
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see if this command returns an error:
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.. code-block:: console
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# virsh create libvirt.xml
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Empty log output for Linux instances
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Problem
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-------
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You can view the log output of running instances
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from either the :guilabel:`Log` tab of the dashboard or the output of
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:command:`nova console-log`. In some cases, the log output of a running
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Linux instance will be empty or only display a single character (for example,
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the `?` character).
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This occurs when the Compute service attempts to retrieve the log output
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of the instance via a serial console while the instance itself is not
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configured to send output to the console.
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Solution
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--------
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To rectify this, append the following parameters to kernel arguments
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specified in the instance's boot loader:
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.. code-block:: ini
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console=tty0 console=ttyS0,115200n8
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Upon rebooting, the instance will be configured to send output to the Compute
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service.
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.. _reset-state:
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Reset the state of an instance
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Problem
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-------
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Instances can remain in an intermediate state, such as ``deleting``.
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Solution
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--------
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You can use the :command:`nova reset-state` command to manually reset
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the state of an instance to an error state. You can then delete the
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instance. For example:
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.. code-block:: console
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$ nova reset-state c6bbbf26-b40a-47e7-8d5c-eb17bf65c485
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$ nova delete c6bbbf26-b40a-47e7-8d5c-eb17bf65c485
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You can also use the :option:`--active` parameter to force the instance back
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to an active state instead of an error state. For example:
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.. code-block:: console
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$ nova reset-state --active c6bbbf26-b40a-47e7-8d5c-eb17bf65c485
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.. _problems-with-injection:
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Injection problems
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~~~~~~~~~~~~~~~~~~
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Problem
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-------
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Instances may boot slowly, or do not boot. File injection can cause this
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problem.
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Solution
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--------
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To disable injection in libvirt, set the following in ``nova.conf``:
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.. code-block:: ini
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[libvirt]
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inject_partition = -2
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.. note::
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If you have not enabled the configuration drive and
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you want to make user-specified files available from
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the metadata server for to improve performance and
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avoid boot failure if injection fails, you must
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disable injection.
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.. _live-snapshotting-fail:
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Disable live snapshotting
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~~~~~~~~~~~~~~~~~~~~~~~~~
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Problem
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-------
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Administrators using libvirt version ``1.2.2`` may experience problems
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with live snapshot creation. Occasionally, libvirt version ``1.2.2`` fails
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to create live snapshots under the load of creating concurrent snapshot.
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Solution
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--------
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To effectively disable the libvirt live snapshotting, until the problem
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is resolved, configure the ``disable_libvirt_livesnapshot`` option.
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You can turn off the live snapshotting mechanism by setting up its value to
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``True`` in the ``[workarounds]`` section of the ``nova.conf`` file:
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.. code-block:: ini
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[workarounds]
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disable_libvirt_livesnapshot = True
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