Arch Linux

donleo

Member

Registered: 2017-02-27

Posts: 3

[SOLVED] Fighting with grub

Hello,
I hope this post is in the right place.

What did I do: I recently changed my Asus laptop (using a 128 GB ssd) to only use Arch with the I3 window manager, but my wife indicated that she also wanted to start using that laptop again, so I decided to change the geometry of the SSD from 3 to 4 partitions to make room for Ubuntu.
I installed Ubuntu 16.10 on /dev/sda4 and let the installation (re-)install grub and its configuration files. I have done this numerous times with many versions of Linux, almost always without issues.

HOWEVER, Ubuntu boots fine, but Arch shows up nicely in the Grub bootmenu, but when booting into Arch I get an error:

Kernel Panic - not syncing VFS: unable to mount root fs to unknown - block (0,0)
etc. with a nice traceback

Now I could use the installation usnstick of Arch and chroot into installed arch , and re-install grub , wich probably will work, but I want to understand what went wrong.

Does anybody have any clue or pointer to more information for me ?

Thanks !

Last edited by donleo (2017-04-11 10:13:26)

Trilby

Inspector Parrot

Registered: 2011-11-29

Posts: 29,531

Website

Re: [SOLVED] Fighting with grub

You should only install grub on one OS or the other, not both.  You can only have one grub install managing the boot process.

If you want to do this from arch, then reinstall grub on arch, follow our wiki, and ask for help if there are troubles booting either arch or ubuntu.  You could then remove the grub package from ubuntu if you want (as it'd be superfluous).

Alternatively, if you want to keep grub managed from ubuntu, you'd really have to ask on the ubuntu forums for help.  I suspect some people here might now whether Ubuntu's grub has os-prober, or how it is similar or different to archlinux's grub package ... but really that's not what these forums are for.

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"UNIX is simple and coherent..." - Dennis Ritchie, "GNU's Not UNIX" -  Richard Stallman

donleo

Member

Registered: 2017-02-27

Posts: 3

Re: [SOLVED] Fighting with grub

Thank you for your response, Trilby. In the many years I have been working and playing with various distributions I have found that one can trust most and have them install grub and the config files as most have a kind of os-prober and will create a nice bootmenu. The only thing sometimes happens is that the default in the menu changes. But some grub installations have the nice property of remembering the last used boot-entry, replacing the default by that last choice.

That is why is was quite surprised by the errors I got, but I re-install grub via arch and os-prober again tomorrow. The only problem might be that if Ubuntu is opdated with a new kernel, at least the boot-menu will be re-created and I might have the same problem again.

Head_on_a_Stick

Member

From: London

Registered: 2014-02-20

Posts: 7,732

Website

Re: [SOLVED] Fighting with grub

The only problem might be that if Ubuntu is opdated with a new kernel, at least the boot-menu will be re-created and I might have the same problem again.

I can't say for sure if this is true for Ubuntu but with Debian the current kernel image & initrd are symlinked to the root directory, you could try adding your own Ubuntu entry to /etc/grub.d/40_custom using the symlinks rather than the numbered versions in /boot (example).

I want to understand what went wrong.

Check the output of `sudo grub-mkconfig` (no arguments) in your Ubuntu system, I seem to remember that their GRUB messes up the Arch entry.

If you wanted to use Ubuntu to "control" GRUB then add Arch to /etc/grub.d/40_custom instead

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Are you infected with Wetiko?

Slithery

Administrator

From: Norfolk, UK

Registered: 2013-12-01

Posts: 5,776

Re: [SOLVED] Fighting with grub

In your situation I'd let Ubuntu handle grub because the Arch kernel always has the same name, whereas the Ubuntu kernel changes name every update. If you let Ubuntu handle grub then it will properly generate the correct configs without any user intervention.

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No, it didn't "fix" anything. It just shifted the brokeness one space to the right. - jasonwryan
Closing -- for deletion; Banning -- for muppetry. - jasonwryan

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donleo

Member

Registered: 2017-02-27

Posts: 3

Re: [SOLVED] Fighting with grub

Ok. For now I solved this by not installing grub with Arch and letting Ubuntu 'manage' grub.cfg. This works fine. So I assume that this can be marked solved.