ZZ from :http://www.linux-noob.com/forums/index.php?/topic/2928-grub-single-boot-and-kernel-panic-reboot/
1.) Booting once-only – (same as lilo -R)
In reference to http://www.gnu.org/s…g-once_002donly
in grub.conf, add the following line to the beginning.
default saved
If for example your grub.conf looks like the one i have below. This boots into the 2.6.20-1.2944 by default.
default=0 timeout=5 splashimage=(hd0,0)/grub/splash.xpm.gz hiddenmenu title Fedora Core (2.6.20-1.2944.fc6) root (hd0,0) kernel /vmlinuz-2.6.20-1.2944.fc6 ro root=LABEL=/ acpi=off initrd /initrd-2.6.20-1.2944.fc6.img title Fedora Core (2.6.20-FluKex.com) root (hd0,0) kernel /vmlinuz-2.6.20-FluKex.com ro root=LABEL=/ acpi=off initrd /initrd-2.6.20-FluKex.com.img
If you want to have it so that 2.6.20-FluKex.com boots on next boot, run the following command from the console before rebooting.
echo “savedefault –default=1 –once” | grub –batch
then
reboot
Now, if you have a kernel that panics and need it to reboot if it panics. change your config and add the panic=# (# being seconds before auto reboot) to the kernel line. Example file below
default=0 timeout=5 splashimage=(hd0,0)/grub/splash.xpm.gz hiddenmenu title Fedora Core (2.6.20-1.2944.fc6) root (hd0,0) kernel /vmlinuz-2.6.20-1.2944.fc6 ro root=LABEL=/ acpi=off panic=5 initrd /initrd-2.6.20-1.2944.fc6.img title Fedora Core (2.6.20-FluKex.com) root (hd0,0) kernel /vmlinuz-2.6.20-FluKex.com ro root=LABEL=/ acpi=off panic=5 initrd /initrd-2.6.20-FluKex.com.img
so the order of operations on this are as follows.
1.) Add new kernel to grub.conf
2.) set default=# in grub.conf to the failsafe kernel (the one you want it to try if the other fails)
3.) run the following:
echo “savedefault –default=1 –once” | grub –batch
4.) reboot