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Re: oxenstored restart after system crash

To: Roger Pau Monne <roger.pau@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>

From: Edwin Torok <edvin.torok@xxxxxxxxxx>

Date: Thu, 18 Feb 2021 10:13:38 +0000

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Cc: Christian Lindig <christian.lindig@xxxxxxxxxx>, Jürgen Groß <jgross@xxxxxxxx>, Ian Jackson <iwj@xxxxxxxxxxxxxx>

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Thread-topic: oxenstored restart after system crash

Hi,

oxenstored doesn't have a tdb file, by default it stores the entire tree in memory only.

There is a way to persistently store the tree (--persistent), but that is not enabled by default and I don't know whether it even works.

Master (or the hotfixed releases) have a live-update functionality now that dump and restore state properly (and reuses some of the persistent disk code, but also dumps some additional state).

The default location of the "persistent" database is /var/run/xenstored, which is a tmpfs and thus cleared on every boot. So if you'd ensure that oxenstored uses the equivalent of that on FreeBSD (or have a script on boot that clears it) that would solve any issues like this.

I don't know about C xenstored's behaviour, I'll let someone else answer that.

Best regards,

--Edwin

From: Roger Pau Monne <roger.pau@xxxxxxxxxx>
Sent: 18 February 2021 09:46
To: xen-devel@xxxxxxxxxxxxxxxxxxxx <xen-devel@xxxxxxxxxxxxxxxxxxxx>
Cc: Christian Lindig <christian.lindig@xxxxxxxxxx>; Edwin Torok <edvin.torok@xxxxxxxxxx>; Jürgen Groß <jgross@xxxxxxxx>; Ian Jackson <iwj@xxxxxxxxxxxxxx>
Subject: oxenstored restart after system crash

Hello,

Last month I got a query from a FreeBSD Xen user having issues with
xenstored after a power failure:

https://lists.freebsd.org/pipermail/freebsd-xen/2021-January/003446.html

I'm not sure what's the right approach here. I've been told cxenstored
will attempt to unlink the tdb file when starting, does oxenstored
attempt to do the same?

Should the tdb file be placed in a path that's cleaned up on boot?

Should xencommons remove the stale tdb before starting xenstored?

Mostly wanted to know what's the approach on Linux so that I can do
the same on FreeBSD.

Thanks, Roger.