grub2 and setting crashkernel kernel argument

Adam Williamson awilliam at
Tue Nov 29 03:31:55 UTC 2011

On Tue, 2011-11-29 at 00:46 +0100, Kevin Kofler wrote:
> Jason L Tibbitts III wrote:
> > You can also edit grub.cfg directly, but it gets wiped out if anything
> > ever runs grub2-mkconfig.  Finally, grubby has options for modifying
> > kernel arguments, but I do not believe that goes in and does anything
> > with the /etc/default/grub line so again that gets wiped out of anything
> > runs grub2-mkconfig.
> But does anything in Fedora actually run grub2-mkconfig automatically? 
> Kernel updates sure don't, they have grubby edit the grub.cfg file directly 
> instead.
> I wonder whether it might actually make sense to patch grub2-mkconfig to no 
> longer emit that warning and to make it a packaging guideline that RPM 
> scriptlets MUST NOT run grub2-mkconfig. The template system may be a nice 
> idea, but it doesn't cover everything, it makes things more complicated, and 
> it doesn't seem to be actually needed in Fedora, thanks to grubby.
> On the other hand, unfortunately, tools such as kcm-grub2, which we probably 
> want to package for Fedora at some point, run grub2-mkconfig, and we can't 
> even blame them for that given that it is what GRUB upstream recommends. :-( 
> (That said, kcm-grub2's KAuth helper's code also scares me for other 
> reasons:
> * The config file to write to is soft-coded as a configuration option, which 
> means that giving out permissions to a user 
> essentially gives that user root. (It doesn't just allow to "Save the GRUB2 
> Bootloader settings" as the action description claims, but to write to ANY 
> file on the system as root.)
> * The executable names to run are hard-coded as grub-*, which is wrong for 
> Fedora.
> IMHO, the proper solution would be to make both of those compile-time CMake 
> options.)
> So the situation is indeed a mess.

Well, it's _something_ of a mess, but as far as end-user customization
goes it is, AFAIK, pretty much always safe just to do things
via /etc/default/grub and grub2-mkconfig, because any changes you
produce in this way will then get inherited by grubby when updating the
kernel, and now everything's in sync.
Adam Williamson
Fedora QA Community Monkey
IRC: adamw | Twitter: AdamW_Fedora | adamwfedora

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