Cannot modify my Grub


I recently switch from Kubuntu to Manjaro :sunglasses: and so I install this last on an other hard drive.
So now I have :

$ lsblk
sda      8:0    0 931,5G  0 disk 
├─sda1   8:1    0   100M  0 part 
├─sda2   8:2    0  73,1G  0 part 
└─sda3   8:3    0 858,3G  0 part 
sdb      8:16   0 931,5G  0 disk 
├─sdb1   8:17   0   7,5G  0 part [SWAP]
├─sdb2   8:18   0  23,3G  0 part 
└─sdb3   8:19   0 900,8G  0 part
sdc      8:32   0 931,5G  0 disk 
├─sdc1   8:33   0   7,8G  0 part [SWAP]
├─sdc2   8:34   0  48,8G  0 part /
└─sdc3   8:35   0 874,9G  0 part /home
sr0     11:0    1  1024M  0 rom

In short :

  • sda - Win7
  • sdb - old Kubuntu
  • sdc - new Manjaro

Sounds simple ? Here the catch.
My old Kubutnu use Btrfs for its / and /home but my new Manjaro use Ext4 for its / and /home.
But when I installed Manjaro, my old Grub wasn't updated :pensive:

I boot on Kubuntu and update it manually :

$ sudo update-grub
$ sudo grub-install /dev/sda

And now, I have a Manjaro entry but when I select it : "Kernel Panic" :frowning:
The only way to boot my Manjaro is to run in in safe mode "initramfs" :thinking:

I switch on Manjaro to force a Grub update and no issue (except my Kubuntu is not reconized but it's not important and probably because of the Btrfs).

But when I reboot, I have the old Kubuntu Grub and no change is done.
So I don't know why my Grub is not updated :confused:

I though of an incompatibility between old Grub and new Grub and maybe erase it (with "dd") before install it would solve the issue but I'm not confident in this solution.

My questions :

  1. Am I right, the Btrfs causes issues with Grub ?
  2. Why Manjaro works in initramfs and not in normal mode ?
  3. How can I fix my Grub for Manjaro ? (the most important one)


The way manjaro (arch) loads the intel microcode via grub is what's causing your issue. Kubuntu doesn't know how to handle this. Grub has to be managed from Manjaro for it to work.

kubuntu handles it well, as does every other OS's. Just that only arch and manjaro handles it 'differently'.

You can boot Manjaro with intel-ucode from Kubuntu's grub using this post from custom.cfg in Kubuntu.

OMG, that's what I meant.

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Ok, thank you for all your anwsers but I figure out I wasn't clear about my goal.

My Kubuntu is old-dead ... I mean, I will remove it very soon. I just kept it for backup and data but once I copy everything on Manajro, I will delete it after. To do that my Manjaro can mount my partition without any issue so it's cool :+1:

So I don't want to fix the Grub made by Kubuntu, I would prefere to remove it and install the new one from Manajro, with the Manajro configuration, etc ... If the new one cannot boot my Kubuntu it's ok, I don't need it anymore.

How can I do that ?

Sorry for the confusion :slightly_smiling_face:

EDIT : but on the other hands, thanks for the explanations, it's far more clear for me now about why I have the issue. Now, I understand it completly :wink:

So make Manjaro grub the default grub.
First boot into Manjaro [1]
Then at Manjaro terminal
sudo grub-install /dev/sda

Where /dev/sda is the primary drive.
If /dev/sdb is the primary drive, do "sudo grub-install /dev/sdb"
If still unsure, what is the primary drive, do all
sudo grub-install /dev/sda
sudo grub-install /dev/sdb
sudo grub-install /dev/sdc
sudo grub-install /dev/sdd

[1] To boot into Manjaro, there's many ways.
Here's one.
Or use Manjaro install media and at install menu, select
"Select other Bootloaders" (or something like that, sorry, I don't install using install media or need one, I've forgotten). That's another way.
Or at kubuntu grub entry for manjaro. modify the last line from
initrd /boot/intel-ucode.img
initrd /boot/initramfs-4.zz-x86_64.img

Ok fixed ! Thank you a lot guys, especially @gohlip :grinning:

I did a grub-install on all my disks and now I have the Manjaro Grub :sunglasses:

But I don't understand something, if my sda is not my primary disk then wich one is ? I always thougth that sda was the primary because 'a' is before 'b' and so on ... how can the computer knows which one is the primary ?

Wrong assumption.

From BIOS boot order. Whichever HD drive is set as first in boot order, controls boot process, so you only need to install Grub to that one. It may usually get "sda" but not always. That's why we always use UUID to point to partitions (in fstab and grub).

Perfect, it's crytal for me now :wink:

Thanks again guys :+1:

IDE has a clear "Master" and "Slave" configuration, this is not true for SATA controllers.

SATA1 is typically default if the onboard SATA controller is selected the first boot device,

However, most UEFI/BIOS systems these days will allow you to choose any detected drive as the boot device, even the IDE Secondary Slave.

SCSI can be even more complicated.

{not to be pedantic, but just an irritating stickler for the facts}

Slot numbering is at the board and, or firmware (bios/uefi) manufacturers discretion.
I've had board that started with 1 and others that started with 0.
I've even seen boards that mark the physical slot as 0 but the firmware listed it as 1.

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:sweat_smile::smile: LOL

I fixed it for your OCD self.
I'm old and i'm tired. LOL..

I've had everything from SMD to ESDI and from ATA to SAS controllers, also probably whatever comes next. I like to play with new shiny things when they come out. :wink:

1 Like

You're just my old sparring partner. :smile:
Welcome back.

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