ironic/install-guide/source/include/kernel-boot-parameters.rst
Mathieu Mitchell 240ee8ffc9 [install-guide] Import "Appending kernel parameters to boot instances"
Import appending kernel parameters to advanced section.

Change-Id: Id688a06ddcdcdfd7dae98e48381f92894825bff8
Partial-bug: #1612278
2016-09-26 08:41:20 -04:00

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.. _kernel-boot-parameters:
Appending kernel parameters to boot instances
---------------------------------------------
The Bare Metal service supports passing custom kernel parameters to boot instances to fit
users' requirements. The way to append the kernel parameters is depending on how to boot instances.
Network boot
============
Currently, the Bare Metal service supports assigning unified kernel parameters to PXE
booted instances by:
* Modifying the ``[pxe]/pxe_append_params`` configuration option, for example::
[pxe]
pxe_append_params = quiet splash
* Copying a template from shipped templates to another place, for example::
https://git.openstack.org/cgit/openstack/ironic/tree/ironic/drivers/modules/pxe_config.template
Making the modifications and pointing to the custom template via the configuration
options: ``[pxe]/pxe_config_template`` and ``[pxe]/uefi_pxe_config_template``.
Local boot
==========
For local boot instances, users can make use of configuration drive
(see :ref:`configdrive`) to pass a custom
script to append kernel parameters when creating an instance. This is more
flexible and can vary per instance.
Here is an example for grub2 with ubuntu, users can customize it
to fit their use case:
.. code:: python
#!/usr/bin/env python
import os
# Default grub2 config file in Ubuntu
grub_file = '/etc/default/grub'
# Add parameters here to pass to instance.
kernel_parameters = ['quiet', 'splash']
grub_cmd = 'GRUB_CMDLINE_LINUX'
old_grub_file = grub_file+'~'
os.rename(grub_file, old_grub_file)
cmdline_existed = False
with open(grub_file, 'w') as writer, \
open(old_grub_file, 'r') as reader:
for line in reader:
key = line.split('=')[0]
if key == grub_cmd:
#If there is already some value:
if line.strip()[-1] == '"':
line = line.strip()[:-1] + ' ' + ' '.join(kernel_parameters) + '"'
cmdline_existed = True
writer.write(line)
if not cmdline_existed:
line = grub_cmd + '=' + '"' + ' '.join(kernel_parameters) + '"'
writer.write(line)
os.remove(old_grub_file)
os.system('update-grub')
os.system('reboot')