On 04/12/2010 11:16 AM, Daniel Veillard wrote:
> Was still missing from main commits and would be needed for 0.8.0
>
> Add documentation for synchronous hooks
>
> * docs/sitemap.html.in: add in navigation under
> Documentation/Deployment/Hooks
> * docs/hooks.html.in: new doc describing current support for 0.8.0
>
> diff --git a/docs/hooks.html.in b/docs/hooks.html.in
> new file mode 100644
> index 0000000..4ebeec3
> --- /dev/null
> +++ b/docs/hooks.html.in
> @@ -0,0 +1,71 @@
> +<?xml version="1.0"?>
> +<html>
> + <body>
> + <h1>Hooks for specific system management</h1>
> + <p>Libvirt includes synchronous hooks starting from version 0.8.0,
> + this is a way to tie specific tailored system actions at specific
^^^^
which
> + time. This is based on scripts being called on the Host where the
> + hypervisor is running, if the script is present when the libvirtd
> + daemon is doing some significant actions.</p>
This last sentence is probably better worded as something like:
"If these scripts are present on the host where the hypervisor is running,
then they are called when the libvirt daemon is doing some significant action."
> + <p>The scripts are expected to execute quickly, return a zero exit
> + status if all conditions are set for the daemon to continue the
> + action (non zero will be considered a failure which may
> + be ignored but in general will stops the ongoing operation).
^^^^^
stop
> + The script also should not call back into libvirt as the daemon
> + is waiting for the script exit and deadlock is likely to occur
> + otherwise.</p>
^^^^^^^^^
s/otherwise//
> + <p>The scripts are stored in the directory <code>/etc/libvirt/hooks/</code>
> + when using a standard installation path
> + (<code>$SYSCONF_DIR/libvirt/hook/</code> in general).</p>
> + <p>The scripts gets arguments as parameter on their command line:</p>
> + <ul>
> + <li> the first argument is the name of the object involved in the
> + operation or '-' if there is none.
> + <li> the second argument is the name of the operation.
> + <li> the third argument is a suboperation indication like 'start'
> + 'end' or '-' if there is none.
> + <li> the last argument is an extra argument string or '-' if there
> + is none.
> + </ul>
> + <p>There is currently scripts for 3 domains of operation:
^^
are
> + <ul>
> + <li><p><code>/etc/libvirt/hooks/daemon</code> script if
> + present is called at 3 points in time:</p>
> + <p>at daemon startup, typically started with the following
> + arguments:</p>
> + <pre>/etc/libvirt/hooks/daemon - start - start</pre>
> + <p>at daemon shutdown when it is about to exit, with the following
> + arguments:</p>
> + <pre>/etc/libvirt/hooks/daemon - shutdown - shutdown</pre>
> + <p>When the daemon is asked to reload its driver state when
> + receiving the SIGHUP signal, arguments are:</p>
> + <pre>/etc/libvirt/hooks/daemon - reload begin SIGHUP</pre>
> + </li>
> + <li><p><code>/etc/libvirt/hooks/qemu</code> script and <br/>
> + <code>/etc/libvirt/hooks/lxc</code> to associate hooks for domain
^^
s/to//
> + operation on the respective QEmu/KVM and LXC drivers.</p>
> + <p> The domain related hooks also receive the full XML description
> + for the concerned domain on their stdin, which allows to get
^
them
> + all the informations from the domain, including UUID or storage
^^^^^^^^^^^^
information
> + if that is needed for the script operation.</p>
> + <p> Currently only domain startup and domain end operations
> + involve the hook, the first one just before the domain gets
> + created.
> + For example if starting a QEmu domain named <code>test</code>
> + the following script will get called:</p>
> + <pre>/etc/libvirt/hooks/qemu test start begin -</pre>
> + <p> note that a non-zero return value from the script will abort the
> + domain startup operation, and if an error string is passed on
> + stderr by the hook script, it will be provided back to the user
> + at the libvirt API level.</p>
> + <p> For domain shutdown, the script will be called just after the
> + domain has finished execution, and the script will get:</p>
> + <pre>/etc/libvirt/hooks/qemu test stopped end -</pre>
> + <p> It is expected that other operation will be associated to hooks
^^^^^^^^^
operations
--
Chris Lalancette
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