Re: Grub2 documentation of the GRUB_CMDLINE_*XEN* parameters -- unclear. What's _intended_?

[Colin Watson]

On Sat, Nov 21, 2015 at 04:12:52PM -0800, PGNet Dev wrote:
> Grub2 documentation @
> https://www.gnu.org/software/grub/manual/grub.html#Configuration states
> 
>       ...
>       ‘GRUB_CMDLINE_XEN’
>       ‘GRUB_CMDLINE_XEN_DEFAULT’
> 
>           The values of these options are appended to the values of
> ‘GRUB_CMDLINE_LINUX’ and ‘GRUB_CMDLINE_LINUX_DEFAULT’ for Linux and Xen menu
> entries.
>       ‘GRUB_CMDLINE_LINUX_XEN_REPLACE’
>       ‘GRUB_CMDLINE_LINUX_XEN_REPLACE_DEFAULT’
> 
>           The values of these options replace the values of 
> ‘GRUB_CMDLINE_LINUX’
> and ‘GRUB_CMDLINE_LINUX_DEFAULT’ for Linux and Xen menu entries.
>       ...
> 
> From these docs. it's not clear which values get mapped to which grub
> entries.  One set 'appends', one set 'replaces'.  Are they exclusive of one
> another?

No, they aren't exclusive of one another, but are used to construct
different command lines.  GRUB_CMDLINE_XEN* are used for the hypervisor
command line; GRUB_CMDLINE_LINUX_XEN_REPLACE* are used for the Linux
kernel command line (but if unset, the corresponding GRUB_CMDLINE_LINUX*
values are used instead).

The misleading description you quote was the one in 2.00, but was
clarified in git a while ago:

  
http://git.savannah.gnu.org/cgit/grub.git/commit/?id=48f39bb4df5b903aaa66db9fdc6679571bff0dd9

> And, what specifically gets mapped to Xen kernel's "options=" parameter
> line?
> 
> E.g., a grub2-mkconfig-generated xen*.cfg takes the form

Upstream grub-mkconfig does not generate xen*.cfg at all.  This is an
openSUSE-specific patch.  From inspecting their source code, I believe
that the GRUB_CMDLINE_XEN* options will apply here.

> The docs should clearly address which PARAMETERS map to the "options=" line,
> and which to the kernel=" line in the Xen case.

No doubt, but it is up to the openSUSE maintainers to make sure that
their patches also include appropriate documentation changes.

-- 
Colin Watson                                       address@hidden