ubuntu - how to add an arch linux entry to efi grub

I have recently installed arch on a disk with windows 7 and Ubuntu on it already. Both the Ubuntu and arch installs are encrypted and I have installed grub to EFI. I can boot arch from BIOS (which then goes to the arch boot partition of the arch install with another grub on it) but there is no entry for it in the ubuntu-generated EFI GRUB (which when I try to update still can't find it even though there is an EFI file in /boot/efi/EFI/arch/grubx64.efi)

How can I add the arch boot partition (with grub on it) to the ubuntu-created one so that when I select in in the Ubuntu one, it goes into the arch grub? (so you can still get into the advanced options part of it)?

Answer

Edit your EFI config file and add a new menu entry:

menuentry "Arch Linux" {
    icon     /EFI/refind/icons/os_arch.png
    volume   BOOT

    loader   /vmlinuz-linux
    initrd   /initramfs-linux.img
    options  "root=/dev/sdbX rootfstype=ext4 rw add_efi_memmap"
    submenuentry "Boot using fallback initramfs" {
        initrd /initramfs-linux-fallback.img
    }
}

I use rEFInd as UEFI boot manager, and my config file path is « /boot/EFI/refind/refind.conf »