How pick up openSUSE kernel command line?

[hallergard]

Grub2 in openSUSE picks up the Kubuntu kernel boot command line, but not the other way around. (I do need the entry "iommu=soft" to boot both distros with USB3)

[jlittle]

In the OS that controls grub, edit /etc/default/grub, and add your entry to the line that says GRUB_CMDLINE_LINUX. If that's Kubuntu, or Suse if it's running KDE, that could be

kdesudo kate /etc/default/grub

The line might then look like GRUB_CMDLINE_LINUX="quiet splash iommu=soft"
Then, run

sudo update-grub

[hallergard]

Thanks, but I have not expessd my question clerly enough. Am using the entry you mention in /etc/default/grub and this works fine for both systems updating their own entry (10_linux). On the Kubuntu menu /boot/grub/grub.cfg the opensuse command line is unchanged, but on the opensuse menu the kubuntu command line is updated.

It seems that on opensuse update-grub 30-os-prober is reading (the updated) command line for kubuntu in kubuntu's grub.cfg!

So I cannot use the Kubuntu menu as default, which I would have preferred, as it does not work for opensuse.

[jlittle]

...It seems that on opensuse update-grub 30-os-prober is reading (the updated) command line for kubuntu in kubuntu's grub.cfg!

I doubted it, but you're right. I've got some old installs from an old machine on a disc I've moved into my new box; I edited the grub.cfg only, to remove a linux parameter, without starting that install, and update-grub picked up the change.

On my 16.04, the call stack is

• update-grub
• /etc/grub.d/30_os-prober
• /usr/bin/linux-boot-prober
• /usr/lib/linux-boot-probes/mounted/50mounted-tests
• /usr/lib/linux-boot-probes/mounted/40grub2

and that parses the grub.cfg.

So, I don't understand why update-grub on your Kubuntu is not finding the parameter you want from Suse's grub.cfg. Maybe there's a grub version mismatch and the parsing by /usr/lib/linux-boot-probes/mounted/40grub2 fails, just guessing. I can run that last script with

/usr/lib/linux-boot-probes/mounted/40grub2 /dev/sdb8 /dev/sdb8 /media/john/vivid/ ext4

(after mounting a volume /dev/sdb8 labelled vivid in dolphin).

When all else fails, one can ignore that complex, frustrating, machinery and hand edit a grub.cfg; it can be much simpler than the generated ones. I did that for years on that old box. I just had a small partition just for grub so that no OS would muck around with it. I think in the long run it was less effort than allowing grub in one of the installs to control the boot.

[hallergard]

Thanks. Kubuntu picks up the command line of Linux Mint and vice versa. Tried borrowing the opensuse 30_os-prober (and editing its /boot/grub2 to /boot/grub) but it did not pick up the opensuse command line.

Yes, I have settled for a manual opensuse entry in 40_Custom which I will have to edit with every opensuse kernel update

[hallergard]

Booted my old 16.04 yesterday, and to my surprise I found that it does pick up the full openSUSE command line (which 16.10 does not). Thought it must be a different version of Grub2, but NO! The same version (2.02~beta2-36ubuntu3.2) is used for my Mint 18 KDE, which does not pick up the openSUSE command line. Thought this was a Kubuntu problem, but now leaning towards it being an openSUSE problem. Have not got a clue though. Anybody?

[hallergard]

Have to modify! Kubuntu and Mint do pick up the openSUSE command line if openSUSE is on a MBR disk, but not if openSUSE is on a GPT disk. Or maybe more correct Legacy install rather than UEFI mode install.