第 21 章 Diagnosing virtual machine problems

Procedure

1. Open the virtqemud.conf file in an editor.

2. Replace or set the filters according to your requirements.

   Expand

   表 21.1. Debugging filter values

   1	logs all messages generated by libvirt.
   2	logs all non-debugging information.
   3	logs all warning and error messages. This is the default value.
   4	logs only error messages.

   Show more

   例 21.1. Sample daemon settings for logging filters

   The following settings:

   • Log all error and warning messages from the remote, util.json, and rpc layers
   • Log only error messages from the event layer.
   • Save the filtered logs to /var/log/libvirt/libvirt.log

   log_filters="3:remote 4:event 3:util.json 3:rpc"
   log_outputs="1:file:/var/log/libvirt/libvirt.log"

3. Save and exit.

4. Restart the libvirt daemon.

   $ systemctl restart virtqemud.service

Procedure

1. Optional: Back up the active set of log filters.

   # virt-admin -c virtqemud:///system daemon-log-filters >> virt-filters-backup

   This makes it possible to restore the active set of filter after generating the logs. If you do not restore the filters, the messages continue to be logged, which may affect system performance.

2. Use the virt-admin utility to enable debugging and set the filters according to your requirements.

   Expand

   表 21.2. Debugging filter values

   1	logs all messages generated by libvirt.
   2	logs all non-debugging information.
   3	logs all warning and error messages. This is the default value.
   4	logs only error messages.

   Show more

   例 21.2. Sample virt-admin setting for logging filters

   The following command:

   • Logs all error and warning messages from the remote, util.json, and rpc layers
   • Logs only error messages from the event layer.

   # virt-admin -c virtqemud:///system daemon-log-filters "3:remote 4:event 3:util.json 3:rpc"

3. Use the virt-admin utility to save the logs to a specific file or directory.

   For example, the following command saves the log output to the libvirt.log file in the /var/log/libvirt/ directory.

   # virt-admin -c virtqemud:///system daemon-log-outputs "1:file:/var/log/libvirt/libvirt.log"

4. Optional: You can also remove the filters to generate a log file that contains all VM-related information. However, it is not recommended since this file may contain a large amount of redundant information produced by libvirt’s modules.

   • Use the virt-admin utility to specify an empty set of filters.

     # virt-admin -c virtqemud:///system daemon-log-filters
       Logging filters:

5. Optional: Restore the filters to their original state by using the backup file that you created previously.

   # virt-admin -c virtqemud:///system daemon-log-filters "<original-filters>"

   In this command, replace <original-filters> with the content of virt-filters-backup.

   Note that if you do not restore the filters, the messages continue to be logged, which may affect system performance.