While installing Arch Linux by following the beginner's guide at https://wiki.archlinux.org/index.php/Beginners%27_Guide , I installed GRUB as my bootloader. However, on rebooting, I find my previous Ubuntu option has disappeared and I am left only with Arch.
I would like to know how I can re-add my other disk partitions to GRUB, as I can find no comprehensible tutorials anywhere else. Thanks.
Boot to archlinux and run as root:
grub-mkconfig -o /boot/grub/grub.cfg
Make sure os-prober is installed if not then install it using:
pacman -S os-prober
Its there in beginner's guide. Read Tip in green color.