On Mon, June 9, 2014 12:57, Steve Clark wrote:

This show how to do a one time boot and then the next time boot the original system

https://www.gnu.org/software/grub/manual/legacy/Booting-once_002donly.html

Thank you. Based on my readings of this reference there are two mechanisms available: 1. boot once, 2. fallback.

The critical step seems to be issuing the command 'grub-set-default n' where n is a value between 0 and the number of entries in boot.conf less one.

Reading the boot-once fallback documentation it recommends fallback as the superior alternative.

<--- Then you may want GRUB to boot the first system which is bootable among `A', `B' and `C'. A configuration file can be written in this way:

default saved # This is important!!! timeout 10 fallback 1 2 # This is important!!!

title A root (hd0,0) kernel /kernel savedefault fallback # This is important!!!

title B root (hd1,0) kernel /kernel savedefault fallback # This is important!!!

title C root (hd2,0) kernel /kernel savedefault

Note that `default saved' (see default), `fallback 1 2' and `savedefault fallback' are used. GRUB will boot the saved entry at index 0 by default and save a fallback entry as next boot entry with this configuration.

When GRUB tries to boot `A', GRUB saves `1' as next boot entry, because the command fallback specifies that `1' is the first fallback entry. The entry `1' is `B', so GRUB will try to boot `B' at next boot time.

Likewise, when GRUB tries to boot `B', GRUB saves `2' as next boot entry, because fallback specifies `2' as next fallback entry. This makes sure that GRUB will boot `C' after booting `B'.

--->

SO a combination of the two boot forms might look like this?:

default saved # This is important!!! timeout 10 fallback 1 2 # This is important!!!

title A root (hd0,0) kernel /kernel savedefault fallback # index is zero

title B root (hd1,0) # assumes a different boot device kernel /kernel savedefault fallback # index is one

title C root (hd2,0) # assumes a third boot device kernel /kernel savedefault # index is two

title the new kernel boot options root (hd0,0) kernel /kernel new_options savedefault 0 # index is three but we save 0 for next boot

I am not sure that I am following the logic of this closely enough to place any reliance in my conclusions but is seems to me that in the last case the command to issue before rebooting is: grub-set-default 3