Re: Serial terminal embedded configuration

[Andrei Borzenkov]

On Mon, Dec 29, 2014 at 4:27 AM, Matthias-Christian Ott <address@hidden> wrote:
> If GRUB's prefix is on an encrypted disk, it prompts for a passphrase
> for the disk. I have an i386 machine without a monitor and without a
> BIOS that can use the serial port as a console and want GRUB to display
> its prompt and read the passphrase from a serial port. Since grub.cfg is
> not loaded without the passphrase the serial port configuration would
> have to be embedded into the core image.
>
> grub-install does not allow to customize the configuration, so I created
> an image via grub-mkimage with the parameters grub-install generated a
> simple serial port configuration similar to the example in the manual
> that works within grub.cfg. Unfortunately it didn't work when embedded
> into the core image.
>
> Is it possible to embed serial port configuration in the core image? If
> so, how do I do it?
>
> Are there plans to support custom embedded configuration in
> grub-install? If not, would patches be accepted?

Please send patches to grub-devel for review and discussion. I think
supporting this makes sense. Even without encrypted $prefix, if user
wants to use serial port we probably should make sure it is available
even in rescue mode.

In practice, the problem is that GRUB_SERIAL_COMMAND can be arbitrary
and serial may need other low level drivers that are available in full
normal mode, but missing in rescue unless explicitly added to
core.img. So some additional parameters for this are needed.

>                                                                      I don't 
> want to
> manually regenerate the core image after each GRUB update when the
> package manager runs grub-install overwrites a core image with the
> embedded configuration.
>
> Regards,
> Matthias-Christian
>
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