1.3 Gentoo - Setup of Bootloader
Overview
I've put together some info on the boot process here
For now this part of the doc will just focus on re-using the kernel included with raspian for the rpi2.
Just to get us booted into gentoo
Mulitple Boot Options
TODO is there any way to have multiple boot options via Noobs? /media/SETTINGS/
Gentoo Setup
Exit chroot
In this case since we're already booting into a Raspian install
we should already have a kernel and modules setup under /boot (/dev/mmcblk0p5) on the sd card
First exit the chroot
exit
Copy Kernel Modules
Next we're going to copy the kernel modules from the raspian setup across to the gentoo root
cp -a /lib/modules /mnt/gentoo/lib/
Edit cmdline.txt
Time to setup the /boot/cmdline.txt to tell the kernel to boot the gentoo system instead of raspian
First lets make a backup of the existing file
cd /boot
cp cmdline.txt cmdline.txt.raspian
Next we're going to edit the file to change the root option to select a different root partition
Original:
dwc_otg.lpm_enable=0 console=ttyAMA0,115200 console=tty1 root=/dev/mmcblk0p6 rootfstype=ext4 elevator=deadline rootwait
New:
dwc_otg.lpm_enable=0 console=ttyAMA0,115200 console=tty1 root=/dev/sda3 rootfstype=ext4 elevator=noop rootwait
Finally make a copy of it
cp cmdline.txt cmdline.txt.gentoo
Now whenever you want to switch between gentoo and raspian just copy one of those files over the top of cmdline.txt
Reboot / Unmount into gentoo
Now we should be ready for booting into gentoo
Use the below commands for unmounting the gentoo filesystem / rebooting into gentoo
umount -l /mnt/gentoo/dev{/shm,/pts,}
umount -l /mnt/gentoo{/proc,/boot,/sys,}
reboot