cant modify grub menu file, need to change boot order

[starkes]

Hey there,

I recently installed a 64-bit version of centOS 5 alongside a 32-bit version, which I use. Turns out the 64-bit version absolutely will not boot and i'm stuck with it as my default boot option.

Since the grub being used resides on the 64-bit half, I cant edit the menu file but I know theres a way to do this without it, through grub itself.

It's a pain in the ass. I have about 29 render nodes now with this problem, and whenever they need to be rebooted I have to hook a monitor up to each one and hold its hand through the boot process.

Can anyone tell me how to change the grub menu through grub itself, basically just change the default boot option and then have it stay that way?


Thanks!

[villager57]

What do you think of changing the order in /boot/grub/grub.conf? Maybe someone can my idea?

ttp://www.redhat.com/docs/manuals/linux/RHL-7.3-Manual/custom-guide/s1-custom-kernel-bootloader.html

[starkes]

i cant get to that file, thats the main problem. I had a dual-boot already with windows and centos5 32-bit, so when the computer starts now, the grub you see is in the 64-bit side that i cant get to.

if you pick centos32 from the menu it falls through to another grub thats inside the 32-bit version. but i need to modify the other (64-bit side) one so it always falls through to the second grub and then to centos32.

i dont really want to fix the 2 grubs problem right now, if it takes any length of time and i have to do it 29 times...yeesh...

[devils casper]

Hi and Welcome !

You have to mount 64bit OS's partition and edit its /boot/grub/grub.conf file. You can edit grub options i GRUB Menu but that will not be preserved on reboot. You have to edit grub.conf file only.
Or
Re-install GRUB of CentOS. Execute this in CentOS 32bit Terminal :

su -
grub-install /dev/sda1

I assumed that /dev/sda1 is / ( or /boot, if any ) partition of CentOS 32bit.

[starkes]

ah! i was just thinking that before you posted, good idea.

is there no way to do it and have the changes be persistent when you edit it through grub itself?

ill try this mounting business out though, thanks

[meton_magis]

you can not. Grub wont write to files, only read them, or edit them for a single boot.

Why didn't you just boot into the 32 bit, and mount the /boot partition of the 64 bit to your filesystem?? then you could edit it there.