Grub Fallback -- Is it for real?

[Janina Sajka]

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
> 
> -- 
> fedora-devel-list mailing list
> fedora-devel-list at redhat.com
> https://www.redhat.com/mailman/listinfo/fedora-devel-list

-- 

Janina Sajka				Phone: +1.240.715.1272
Partner, Capital Accessibility LLC	http://www.CapitalAccessibility.Com

Marketing the Owasys 22C talking screenless cell phone in the U.S. and Canada--Go to http://www.ScreenlessPhone.Com to learn more.

Chair, Accessibility Workgroup		Free Standards Group (FSG)
janina at freestandards.org		http://a11y.org