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8.6 Using Lock Files
When working with several VM Host Server systems that may run a pool of guests, a
common task is to ensure that the guest systems are not started twice. Depending on
the used block and network devices, this could lead to network problems as well as
corrupted block devices.
Xen provides a mechanism that checks a lock file before a guest is started. In order to
use this mechanism, a distributed file system like NFS or a cluster file system is needed.
For example, a distributed file system mounted to /srv/xen may be used.
The Xen domain lock functionality is configured in the Xend configuration file /etc/
xen/xend-config.sxp. At the end of this file, the two parameters
xend-domain-lock and xend-domain-lock-path control the behavior. To
use the directory /srv/xen as locking directory, modify the settings as follows:
(xend-domain-lock yes)
(xend-domain-lock-path /xen/lock)
Activate the new settings either by rebooting the VM Host Server system, or by
restarting xend with the command rcxend restart.
When all VM Host Server systems use this locking directory, Xen will refuse to start
a VM Guest twice.
8.7 HVM Features
In Xen some features are only available for fully virtualized domains. They are not very
often used, but still may be interesting in some environments.
8.7.1 Specify Boot Device on Boot
Just as with physical hardware, it is sometimes desirable to boot a VM Guest from a
different device than its own boot device. For fully virtual machines, the managing
program virt-manager provides a possibility to achieve this.
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Virtualization with Xen
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