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libvirt/docs/format.html.in
Eric Blake 252958ee16 backup: Document new XML for backups
Prepare for new backup APIs by describing the XML that will represent
a backup.  The XML resembles snapshots and checkpoints in being able
to select actions for a set of disks, but has other differences.  It
can support both push model (the hypervisor does the backup directly
into the destination file) and pull model (the hypervisor exposes an
access port for a third party to grab what is necessary).  Add
testsuite coverage for some minimal uses of the XML.

The <disk> element within <domainbackup> tries to model the same
elements as a <disk> under <domain>, but sharing the RNG grammar
proved to be hairy. That is in part because while <domain> use
<source> to describe a host resource in use by the guest, a backup job
is using a host resource that is not visible to the guest: a push
backup action is instead describing a <target> (which ultimately could
be a remote network resource, but for simplicity the RNG just
validates a local file for now), and a pull backup action is instead
describing a temporary local file <scratch> (which probably should not
be a remote resource).  A future refactoring may thus introduce some
way to parameterize RNG to accept <disk type='FOO'>...</disk> so that
the name of the subelement can be <source> for domain, or <target> or
<scratch> as needed for backups. Future patches may improve this area
of code.

Signed-off-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
2019-12-10 12:41:56 +01:00

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XML

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<body>
<h1>XML Format</h1>
<p>
Objects in the libvirt API are configured using XML documents to allow
for ease of extension in future releases. Each XML document has an
associated Relax-NG schema that can be used to validate documents
prior to usage.
</p>
<ul>
<li><a href="formatdomain.html">Domains</a></li>
<li><a href="formatnetwork.html">Networks</a></li>
<li><a href="formatnwfilter.html">Network filtering</a></li>
<li><a href="formatnetworkport.html">Network ports</a></li>
<li><a href="formatstorage.html">Storage</a></li>
<li><a href="formatstorageencryption.html">Storage encryption</a></li>
<li><a href="formatcaps.html">Capabilities</a></li>
<li><a href="formatdomaincaps.html">Domain capabilities</a></li>
<li><a href="formatstoragecaps.html">Storage Pool capabilities</a></li>
<li><a href="formatnode.html">Node devices</a></li>
<li><a href="formatsecret.html">Secrets</a></li>
<li><a href="formatsnapshot.html">Snapshots</a></li>
<li><a href="formatcheckpoint.html">Checkpoints</a></li>
<li><a href="formatbackup.html">Backup jobs</a></li>
</ul>
<h2>Command line validation</h2>
<p>
The <code>virt-xml-validate</code> tool provides a simple command line
for validating XML documents prior to giving them to libvirt. It uses
the locally instaled RNG schema documents. It will auto-detect which
schema to use for validation based on the name of the top level element
in the input document. Thus it merely requires the XML document filename
to be passed on the command line
</p>
<pre>
$ virt-xml-validate /path/to/XML/file</pre>
</body>
</html>