Hi,

I have a XEN guest which fails to come up.

It's no drama at this point since I had a backup of the guest, however I'd
like to understand why it failed and has never been able to come up again. 

If possible, I'd also like to understand how to trouble-shoot such problems.

Basically, the XEN guest had a problem where the websites it was hosting
stopped responding. Getting in via ssh I noticed a bunch of "read only
filesystem" errors.

I rebooted it, filesystems checked ok and journals committed, but it sits at
this point on the console:

SELinux:  Disabled at runtime.
SELinux:  Unregistering netfilter hooks
type=1404 audit(1248725516.191:2): selinux=0 auid=4294967295 ses=4294967295

and never brings up the login prompt.

I can issue:

xm shutdown <guest>

and it does shut itself down.

It's an SL 5.3 guest (32bit) running on an SL 5.3 host (32bit).

At the point above, no networking works so the guest is effectively cactus.

I am able to mount the img using loop back, kpartx etc and the filesystem is
in tact, checking logs I can't see anything obvious as to why it never comes
up. I've even tried booting into the older kernel of the guest.

This only started happening after I applied the following patches:

Jul 25 06:59:30 server yum: Updated: xulrunner-1.9.0.12-1.el5_3.i386
Jul 25 06:59:32 server yum: Updated:
tomcat5-servlet-2.4-api-5.5.23-0jpp.7.el5_3.2.i386
Jul 25 06:59:48 server yum: Updated: libtiff-3.8.2-7.el5_3.4.i386
Jul 25 06:59:59 server yum: Updated: firefox-3.0.12-1.el5_3.i386
Jul 25 07:00:03 server yum: Updated:
tomcat5-jsp-2.0-api-5.5.23-0jpp.7.el5_3.2.i386

Prior to that reboots would work fine.

I have several XEN guests under SL 5.3 and from the experience above I'm
skeptical now whether I should rely on XEN outside of test environments.

What's an effective way to trouble-shoot the above type of problem to try and
understand what is going wrong?

Thanks.

Michael.