I would like to dual boot ArchLinux with my Ubuntu. I would like some hints at how to do it without messing my partitions too much. Presently, my Computer partition scheme goes like this:

(Ubuntu only)
    sda1    [boot loader]
    sda2    [root]
    sda3    [swap]
    sda4    [home]

If I were to install Arch only, I would have the same partition scheme. Now how should I prepare my partitions in order to successfully dual-boot? I have a suggestion though it may be a naive one:

    sda1    [bootloader]  -> Will it detect Arch?
    sda2    [root_ubuntu]
    sda3    [swap]
    sda4    [home_ubuntu] -> I have a lot of space, I could just resize and divide this partition.
    sda5    [root_arch]
    sda6    [home_arch]

Will the above scheme be a workable implementation? In any case, what do you suggest I do? Which files (config, etc) will I have to create or modify?

  • Have you thought about installing Arch into a chroot? – StrongBad Apr 27 '15 at 11:15
  • I did pretty much exactly this, except I also had a Windows partition. I decided to keep GRUB from Ubuntu, and that also worked fine. – Sparhawk Apr 27 '15 at 11:20
  • @StrongBad: No I haven't. It seems to be a good idea. Should I understand I could install arch on an USB partition, then from Ubuntu I could mount it, then using chroot to the mounted USB partition... Would that work? – kaligne Apr 27 '15 at 11:24
  • @user3298319 yes, see my answer. – StrongBad Apr 27 '15 at 11:38

This scheme is certainly workable. You are right, the best solution is to transform your current layout as little as it is possible.

If you don't ask Arch Linux to install his Grub bootloader, you'll have to run grub-mkconfig -o /boot/grub/grub.cfg in Ubuntu (if you have os-prober installed, it will find your Arch installation and update all the config files automatically).

You may find information you need about Grub in Arch Linux wiki: https://wiki.archlinux.org/index.php/GRUB (almost all the instuctions are applicable to current versions of Ubuntu)

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While dual booting is a useful concept to allow you to use both Windows and Linux on the same machine, the benefits of dual booting Linux are more subtle. The boot process in Linux typically involves using a boot loader to load a kernel and ram disk which eventually mounts the root file system and lets you do things. Different distros have different kernels, and many distros patch the kernel to different extents. If you wish to run two different kernels, either for the same distro or different distros, then you need to dual boot. If you are happy with the same kernel, you generally do not need to dual boot to be able to run two different Linux distributions, you can just create a chroot for each additional distribution. The Arch wiki has nice articles on Arch chroot and installing chroot.

One advantage, based on your comments, of using a chroot, is you could do a fully bootable USB install of Arch and then simply chroot into it under most circumstances. This means you would not need to change the main hard disk (sda) at all.

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  • Thank you for the explanations. If I want to use a GUI (gnome) with ArchLinux this way, I guess I would have to configure X everytime the USB stick is plugged into a computer with a differing video card right? – kaligne Apr 27 '15 at 14:37
  • @user3298319 I have a USB stick install with LXDE (but I don't think Gnome would be different) and X auto detects simple single monitor setups (e.g., laptop and desktop). For dual monitor setups, rotated monitors, or other cases where the monitor is not correctly identified, I need to use xrandr or the graphical monitor manager to setup the monitor. Haven't had too much of a problem with using the open source drivers. – StrongBad Apr 27 '15 at 14:46
  • That sounds so promising, I'll give it a try tonight or tomorrow ! =) – kaligne Apr 27 '15 at 15:46
  • Ok I cloned my arch_root and arch_home partitions on a partitioned usb thumb stick. Now then logged in on my Ubuntu. I mounted arch_root partition in /mnt and arch_home partition in /mnt/home . My arch_user home directory is in /mnt/home/ . I used chroot /mnt. How do I log in my arch_user account ? – kaligne Apr 28 '15 at 19:01

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