I have an ubuntu and archlinux multiboot system. The grub is installed by the ubuntu system. So, it is grub 2. I want to set the nomodeset for the arch boot. I am unable to set it permanently.
I cannot edit /boot/grub/grub.cfg as it is autogenerated
Editing /etc/default/grub not working as well (as it changes only the Ubuntu setting)
Any ideas?

os-proberif you don't have custom menu entry. You may try to edit30_os-proberfile in/etc/grub.d/from line 229. – sagarchalise Feb 16 '12 at 8:14