purpose of /var/lib/xend/state

purpose of /var/lib/xend/state

[John Levon]

What are these XML files actually for? I don't understand why this
information needs to persist - can somebody explain the reason?

When these files become corrupted for whatever reason, xend fails to
start altogether. At the very least, this needs to be made more robust
(I may work on a patch for this once I understand this stuff better).

regards,
john

Re: purpose of /var/lib/xend/state

[John Levon]

On Fri, Dec 07, 2007 at 03:48:48PM +0000, John Levon wrote:

> What are these XML files actually for? I don't understand why this
> information needs to persist - can somebody explain the reason?

Hrm, it seems like at least the pif files are for some Linux
configuration thing via the Xen API. Is there really nowhere on Linux
itself to store this stuff?

I'm looking at host.xml and it's got me worried - what happens if I
change the hostname?

What happens if I modify storage stuff outside of the xen api? Is xend
supposed to cope?

Storing info in two places is rarely a good idea :/

regards
john

Re: purpose of /var/lib/xend/state

[Daniel P. Berrange]

On Fri, Dec 07, 2007 at 03:48:48PM +0000, John Levon wrote:
> 
> What are these XML files actually for? I don't understand why this
> information needs to persist - can somebody explain the reason?
> 
> When these files become corrupted for whatever reason, xend fails to
> start altogether. At the very least, this needs to be made more robust
> (I may work on a patch for this once I understand this stuff better).

Its a serious pain wrt to networking. At startup XenD scans all active
network interfaces and saves a record of them. Next-time you start XenD
it will re-create any that it previously saw.

This is exceedingly bad for interfaces/bridges managed by the distro
init scripts. eg, if I had a bridge configured and then remove its
config, XenD will now happily re-create this bridge itself.  I've got
a patch pending to make XenD leave any externally managed PIFs alone
only touching one it created itself via XenAPI

Dan.
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