[Solved] Dual UEFI Booting Arch against pre-existing Ubuntu install

Question

Hi All,
I'm new to Arch Linux and have just managed to install it on my T530 Lenovo laptop along side a pre-existing Ubuntu installation.
However, although I did consult the dual boot posting and article here on the site beforehand, those articles seemed to be about installing Grub. Since I already have it up and working, I was nervous about deleting it and so potentially loosing my working Ubuntu installation.
I tried installing mounting my pre existing /boot/efi partition but the pre-existing vmlinuz-linux file (no doubt from my Ubuntu installation) prevented it from working. My solution was to create the boot folder on the same partition as my Arch installation.
I now have an installation that works (kind of) however, it appears each time I boot up, I have to edit the Grub entry for my Arch installation to update the UUID Grub points to to get it to load up Arch. I can't find where the actual file being loaded in Grub resides (the file that it appears generates this script, is itself built from a series of predefined variables).
I admit I am playing at the moment - I'm keen to get to grips with this distro and am up for considering all options including deleting and starting again to learn to get it set up correctly. My questions are:
How should I have done this so that my Arch linux distro was loaded via Grub called by the UEFI and had the same booting file structure as the already existing Ubuntu installation (using the BOOTLOADER partition and the /boot/efi folders on it)
How do I edit the Grub file for my Arch distro so it stays edited (no more retyping all the UUIDs each time I load it up
Is there a way to get to the installation I currently have to an the more ideal state
Details taken thanks to the bootrepair application are here:
http://paste.ubuntu.com/10682898/
Thanks and regards,
Simon
Last edited by simon_sjw (2015-04-22 11:50:52)

Answer 1

I don't think there are any Ubuntu kernel images on your EFI system partition (they are in /boot, not /boot/efi).
If you want Arch to boot in an EFI system you should mount /boot (rather than /boot/efi) to the EFI system partition.
To do this, copy the /boot folder over to /dev/sda1 and add it to your /etc/fstab (in Arch):
/dev/sda1 /boot vfat rw,relatime,discard,nodev,nosuid,noexec,fmask=0022,dmask=0022,codepage=437,iocharset=iso8859-1,shortname=mixed,errors=remount-ro 0 2
It's probably best to install & configure GRUB from Arch rather than Ubuntu because Arch mounts /boot to the ESP while all other distributions mount /boot/efi so the results may get confusing (ie, GRUB may create menu entries to boot Ubuntu with your Arch kernel and vice versa); also the Arch kernel image is booted read-write whereas most other kernel images are booted read-only.
https://wiki.archlinux.org/index.php/GRUB#UEFI_systems
I find the os-prober script can fail sometimes so this is probably your problem here.
Personally, I use gummiboot to boot my Debian system by copying the kernel image & initial ramdisk to the EFI system partition using these commands in Debian (this would also work in Ubuntu):
# mount /dev/sda1 /mnt
# cp /vmlinuz /initrd.img /mnt
Then I make a gummiboot menu entry; your Ubuntu entry would look like this:
title Ubuntu
linux /vmlinuz
initrd /initrd.img
options root=/dev/sda2 ro
Add any kernel parameters after "ro" and make an entry for Arch as well (you may also need to configure /boot/loader/loader.conf as per the ArchWiki page) & install gummiboot from Arch using:
# gummiboot install
You can then create a post-install script at /etc/kernel/postinst.d/zz-update-gummiboot in your Ubuntu system to copy over the kernel image & initrd to the ESP whenever the kernel is updated:
#!/bin/sh
mount /dev/sda1 /mnt
cp /vmlinuz /initrd.img /mnt/
umount -R /mnt
Make this executable:
# chmod +x /etc/kernel/postinst.d/zz-update-gummiboot
This method will only work if you have /boot mounted to the EFI system partition (as outlined in the Beginner's Guide).