Synnefo » snf-ganeti » ganeti-local

Instance kernel selection

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The kernel that instances uses to bootup can come either from the node,

or from instances themselves, depending on the setup.

Xen-PVM

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With Xen PVM, there are three options.

First, you can use a kernel from the node, by setting the hypervisor

parameters as such:

- ``kernel_path`` to a valid file on the node (and appropriately

  ``initrd_path``)

- ``kernel_args`` optionally set to a valid Linux setting (e.g. ``ro``)

- ``root_path`` to a valid setting (e.g. ``/dev/xvda1``)

- ``bootloader_path`` and ``bootloader_args`` to empty

Alternatively, you can delete the kernel management to instances, and

use either ``pvgrub`` or the deprecated ``pygrub``. For this, you must

install the kernels and initrds in the instance, and create a valid grub

v1 configuration file.

For ``pvgrub`` (new in version 2.4.2), you need to set:

- ``kernel_path`` to point to the ``pvgrub`` loader present on the node

  (e.g. ``/usr/lib/xen/boot/pv-grub-x86_32.gz``)

- ``kernel_args`` to the path to the grub config file, relative to the

  instance (e.g. ``(hd0,0)/grub/menu.lst``)

- ``root_path`` **must** be empty

- ``bootloader_path`` and ``bootloader_args`` to empty

While ``pygrub`` is deprecated, here is how you can configure it:

- ``bootloader_path`` to the pygrub binary (e.g. ``/usr/bin/pygrub``)

- the other settings are not important

More information can be found in the Xen wiki pages for `pvgrub

<http://wiki.xensource.com/xenwiki/PvGrub>`_ and `pygrub

<http://wiki.xensource.com/xenwiki/PyGrub>`_.

KVM

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For KVM also the kernel can be loaded either way.

For loading the kernels from the node, you need to set:

- ``kernel_path`` to a valid value

- ``initrd_path`` optionally set if you use an initrd

- ``kernel_args`` optionally set to a valid value (e.g. ``ro``)

If you want instead to have the instance boot from its disk (and execute

its bootloader), simply set the ``kernel_path`` parameter to an empty

string, and all the others will be ignored.