diskimage-builder/diskimage_builder/elements/bootloader/README.rst
Ian Wienand f6a2452d4c Only append DIB_BOOTLOADER_DEFAULT_CMDLINE to default grub entry
The grub.cfg has two variables [1]

 GRUB_CMDLINE_LINUX : used on all boots
 GRUB_CMDLINE_LINUX_DEFAULT : additionally used on all "normal" boots

The problem with I2298675dda1f699c572b3423e7274bc8bd7c1c9d is that it
appened the values in DIB_BOOTLOADER_DEFAULT_CMDLINE to both of these,
resulting in duplicated arguments.  I don't think we considered that
GRUB_CMDLINE_LINUX_DEFAULT actually already appends to the
GRUB_CMDLINE_LINUX values.

Make DIB_BOOTLOADER_DEFAULT_CMDLINE only append itself to
GRUB_CMDLINE_LINUX_DEFAULT.  That seems to line up sensibly with the
name of the variable.

Documentation is enhanced around this, and a releasenote added.

[1] https://help.ubuntu.com/community/Grub2/Setup

Change-Id: I76b5442a9090c19a6540ed2d4ab324546f241ebf
Closes: #1791736
2018-09-13 09:51:50 +10:00

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==========
bootloader
==========
Installs ``grub[2]`` on boot partition on the system. In case GRUB2 is
not available in the system, a fallback to Extlinux will happen. It's
also possible to enforce the use of Extlinux by exporting a
``DIB_EXTLINUX`` variable to the environment.
Arguments
=========
* ``DIB_GRUB_TIMEOUT`` sets the ``grub`` menu timeout. It defaults to
5 seconds. Set this to 0 (no timeout) for fast boot times.
* ``DIB_BOOTLOADER_DEFAULT_CMDLINE`` sets parameters that are appended
to the ``GRUB_CMDLINE_LINUX_DEFAULT`` values in ``grub.cfg``
configuration. It defaults to ``nofb nomodeset vga=normal``.