Grub Fallback -- Is it for real?
Janina Sajka
janina at rednote.net
Mon Mar 13 23:36:17 UTC 2006
Warren Togami writes:
> Janina Sajka wrote:
> >
> >Should I expect this to work? Is there some other mechanism to boot a
> >different kernel just once--on the next boot?
>
> http://togami.com/~warren/guides/remoteraidcrazies/
> My guide here has an example of using grub's savedefault --default X
> --once directives in order to specify a kernel to boot next. It tries
> to boot that kernel. If you reboot again, it falls back to the first
> listed kernel in grub.conf.
>
Hmmm, this syntax looks different from that in the grub docs on gnu.org.
Thanks for forwarding this. I will study and see what I can do with it.
I am precisely in the position of needing to manage a server which I
cannot get to physically.
Janina
> In order to use this type of fallback, you need to move your "known
> good" kernel to be in the first position. Then change
> /boot/grub/grub.conf so "default=saved". Then savedefault --default X
> --once chooses a kernel specified by X, which begins counting at zero.
>
> I personally use savedefault --default X --once on my dedicated server
> where I have no physical access, but I do have remote power cycling
> capability. This way I can reboot into an experimental kernel, and
> trigger a reboot into the original kernel if it got "stuck" during bootup.
>
> Another option is to use "panic=X" where X is a number of seconds. This
> triggers an automatic reboot if the kernel panics. It doesn't always
> work, but might be useful in some cases where you don't have physical
> access to the box. I personally don't use panic=X anymore after I
> gained remote power cycling capability.
>
> Warren Togami
> wtogami at redhat.com
>
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--
Janina Sajka Phone: +1.240.715.1272
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