migration.html: Clarify configuration file handling docs

Migration never removes any configuration files on the destination host.
Thus when the domain is already defined on the destination, it will stay
persistent even after migration without --persist.

https://bugzilla.redhat.com/show_bug.cgi?id=1514930

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
This commit is contained in:
Jiri Denemark 2017-12-08 10:31:38 +01:00
parent ce73de441d
commit 2c01e4febc

View File

@ -206,14 +206,14 @@
<h2><a id="config">Configuration file handling</a></h2> <h2><a id="config">Configuration file handling</a></h2>
<p> <p>
There are two types of virtual machine known to libvirt. A <em>transient</em> There are two types of virtual machines known to libvirt. A <em>transient</em>
guest only exists while it is running, and has no configuration file stored guest only exists while it is running, and has no configuration file stored
on disk. A <em>persistent</em> guest maintains a configuration file on disk on disk. A <em>persistent</em> guest maintains a configuration file on disk
even when it is not running. even when it is not running.
</p> </p>
<p> <p>
By default, a migration operation will not attempt to change any configuration By default, a migration operation will not attempt to modify any configuration
files that may be stored on either the source or destination host. It is the files that may be stored on either the source or destination host. It is the
administrator, or management application's, responsibility to manage distribution administrator, or management application's, responsibility to manage distribution
of configuration files (if desired). It is important to note that the <code>/etc/libvirt</code> of configuration files (if desired). It is important to note that the <code>/etc/libvirt</code>
@ -230,14 +230,14 @@
host and removed on the original. host and removed on the original.
</li> </li>
<li>Centralized configuration files outside libvirt, in a database. A data center <li>Centralized configuration files outside libvirt, in a database. A data center
management application may not storage configuration files at all. Instead it management application may not store configuration files at all. Instead it
may generate libvirt XML on the fly when a guest is booted. It will typically may generate libvirt XML on the fly when a guest is booted. It will typically
use transient guests, and thus not have to consider configuration files during use transient guests, and thus not have to consider configuration files during
migration. migration.
</li> </li>
<li>Distributed configuration inside libvirt. The configuration file for each <li>Distributed configuration inside libvirt. The configuration file for each
guest is copied to every host where the guest is able to run. Upon migration guest is copied to every host where the guest is able to run. Upon migration
the existing config merely needs to be updated with any changes the existing config merely needs to be updated with any changes.
</li> </li>
<li>Ad-hoc configuration management inside libvirt. Each guest is tied to a <li>Ad-hoc configuration management inside libvirt. Each guest is tied to a
specific host and rarely migrated. When migration is required, the config specific host and rarely migrated. When migration is required, the config
@ -246,7 +246,7 @@
</ul> </ul>
<p> <p>
As mentioned above, libvirt will not touch configuration files during As mentioned above, libvirt will not modify configuration files during
migration by default. The <code>virsh</code> command has two flags to migration by default. The <code>virsh</code> command has two flags to
influence this behaviour. The <code>--undefine-source</code> flag influence this behaviour. The <code>--undefine-source</code> flag
will cause the configuration file to be removed on the source host will cause the configuration file to be removed on the source host
@ -265,12 +265,12 @@
<th colspan="3">After migration</th> <th colspan="3">After migration</th>
</tr> </tr>
<tr class="subhead"> <tr class="subhead">
<th>Guest type</th> <th>Source type</th>
<th>Source config</th> <th>Source config</th>
<th>Dest config</th> <th>Dest config</th>
<th>--undefine-source</th> <th>--undefine-source</th>
<th>--persist</th> <th>--persist</th>
<th>Guest type</th> <th>Dest type</th>
<th>Source config</th> <th>Source config</th>
<th>Dest config</th> <th>Dest config</th>
</tr> </tr>
@ -325,9 +325,9 @@
<td class="y">Y</td> <td class="y">Y</td>
<td class="n">N</td> <td class="n">N</td>
<td class="n">N</td> <td class="n">N</td>
<td>Transient</td> <td>Persistent</td>
<td class="n">N</td>
<td class="n">N</td> <td class="n">N</td>
<td class="y">Y<br/>(unchanged dest config)</td>
</tr> </tr>
<tr> <tr>
<td>Transient</td> <td>Transient</td>
@ -335,9 +335,9 @@
<td class="y">Y</td> <td class="y">Y</td>
<td class="y">Y</td> <td class="y">Y</td>
<td class="n">N</td> <td class="n">N</td>
<td>Transient</td> <td>Persistent</td>
<td class="n">N</td>
<td class="n">N</td> <td class="n">N</td>
<td class="y">Y<br/>(unchanged dest config)</td>
</tr> </tr>
<tr> <tr>
<td>Transient</td> <td>Transient</td>
@ -347,7 +347,7 @@
<td class="y">Y</td> <td class="y">Y</td>
<td>Persistent</td> <td>Persistent</td>
<td class="n">N</td> <td class="n">N</td>
<td class="y">Y</td> <td class="y">Y<br/>(replaced with source)</td>
</tr> </tr>
<tr> <tr>
<td>Transient</td> <td>Transient</td>
@ -357,7 +357,7 @@
<td class="y">Y</td> <td class="y">Y</td>
<td>Persistent</td> <td>Persistent</td>
<td class="n">N</td> <td class="n">N</td>
<td class="y">Y</td> <td class="y">Y<br/>(replaced with source)</td>
</tr> </tr>
<!-- src:Y dst:N --> <!-- src:Y dst:N -->
@ -411,7 +411,7 @@
<td class="n">N</td> <td class="n">N</td>
<td>Persistent</td> <td>Persistent</td>
<td class="y">Y</td> <td class="y">Y</td>
<td class="y">Y</td> <td class="y">Y<br/>(unchanged dest config)</td>
</tr> </tr>
<tr> <tr>
<td>Persistent</td> <td>Persistent</td>
@ -421,7 +421,7 @@
<td class="n">N</td> <td class="n">N</td>
<td>Persistent</td> <td>Persistent</td>
<td class="n">N</td> <td class="n">N</td>
<td class="y">Y</td> <td class="y">Y<br/>(unchanged dest config)</td>
</tr> </tr>
<tr> <tr>
<td>Persistent</td> <td>Persistent</td>
@ -431,7 +431,7 @@
<td class="y">Y</td> <td class="y">Y</td>
<td>Persistent</td> <td>Persistent</td>
<td class="y">Y</td> <td class="y">Y</td>
<td class="y">Y</td> <td class="y">Y<br/>(replaced with source)</td>
</tr> </tr>
<tr> <tr>
<td>Persistent</td> <td>Persistent</td>
@ -441,7 +441,7 @@
<td class="y">Y</td> <td class="y">Y</td>
<td>Persistent</td> <td>Persistent</td>
<td class="n">N</td> <td class="n">N</td>
<td class="y">Y</td> <td class="y">Y<br/>(replaced with source)</td>
</tr> </tr>
</tbody> </tbody>
</table> </table>