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Re: [Xen-users] How to stop yum update on CentOS 5.1 to modify grub

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Subject: Re: [Xen-users] How to stop yum update on CentOS 5.1 to modify grub
From: Mark Williamson <mark.williamson@xxxxxxxxxxxx>
Date: Sun, 13 Apr 2008 16:49:35 +0100
Cc: Rudi Ahlers <Rudi@xxxxxxxxxxx>, Bas Mevissen <abuse@xxxxxxxxxxxxxx>
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> > I've installed an IPMI2 module in my server. Costs about Eur 50 and
> > gives you remote monitors (temperature, fans) and serial port-like
> > console. Saved me a few trips to the DC already.
> >
> >> I guess I'll just exclude the normal kernel from the updates as you
> >> suggest. P.S. Do you know if one could set a backup / fail-safe
> >> kernel in grub, which can automatically boot if thew default kernel
> >> gives problems?
> >
> > Just set UPDATEDEFAULT to "yes" if you want the latest Xen kernel by
> > default and to "no" otherwise. Set DEFAULTKERNEL to "kernel-xen" and
> > simply leave that other kernel around.
> >
> > Grub is no watchdog. So it cannot detect boot failure. If you want
> > something like that, arrange a budget and contact me :-)
> >
> > Bas.
> Hi Bas
> Unfortunately things work a lot different in our country. I'd like to
> take up your offer on the watchdog, but I know I won't be able to afford
> it, especially if you say I need to budget for it. Our currency is about
> 8times the USD, so for USD100 I need to pay USD800 - which is a lot. And
> then we still need to pay for import duties, etc. Quite often, the
> USD100 components end up costing us about USD300's value.
> P.S. What is IPMI2? Will it work on standard Pentium IV grade
> motherboards, or only on Xeon server grade motherboards? And does it get
> installed on the inside of the server, or how does it work?

Grub can do some useful high availability things; you can set a fallback 
kernel in case the default fails to load at all.

You can also set up grub so that it will only choose a particular item *if* on 
the previous boot the system managed to get fully booted and ran a 
user-specified script to modify grub's next boot settings.

This way you can ensure that if a system reboots before your grub update 
script gets run then the next boot will choose a safe fallback boot option.  
I set this up on one of my systems once.


Push Me Pull You - Distributed SCM tool (http://www.cl.cam.ac.uk/~maw48/pmpu/)

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