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Move dracut docs to their own heading

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Signed-off-by: Jonathon Anderson <janderson@ciq.com>
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Jonathon Anderson
2024-07-15 11:57:09 -06:00
parent 1e17b816c5
commit 527ab6249e
1 changed files with 76 additions and 75 deletions
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userdocs/contents/boot-management.rst
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@@ -32,81 +32,6 @@ Booting with iPXE
ipxe_cfg->kernel[ltail=cluster0,label="http"];
}
Booting with dracut
-------------------
Some systems, typically due to limitations in their BIOS or EFI
firmware, are unable to load container image of a certain size
directly with a traditional bootloader, either iPXE or GRUB. As a
workaround for such systems, Warewulf can be configured to load a
dracut initramfs from the container and to use that initramfs to load
the full container image.
Warewulf provides a dracut module to configure the dracut initramfs to
load the container image. This module is available in the
``warewulf-dracut`` subpackage, which must be installed in the
container image.
With the ``warewulf-dracut`` package installed, you can build an
initramfs inside the container.
.. code-block:: shell
dnf -y install warewulf-dracut
dracut --force --no-hostonly --add wwinit --kver $(ls /lib/modules | head -n1)
Set the node's iPXE template to ``dracut`` to direct iPXE to fetch the
node's initramfs image and boot with dracut semantics, rather than
booting the node image directly.
.. note::
Warewulf iPXE templates are located at ``/etc/warewulf/ipxe/`` when
Warewulf is installed via official packages. You can learn more
about how dracut booting works by inspecting its iPXE template at
``/etc/warewulf/ipxe/dracut.ipxe``.
.. code-block:: shell
wwctl node set wwnode1 --ipxe dracut
.. note::
The iPXE template may be set at the node or profile level.
Alternatively, to direct GRUB to fetch the node's initramfs image and boot with
dracut semantics, set a ``GrubMenuEntry`` tag for the node.
.. note::
Warewulf configures GRUB with a template located at
``/etc/warewulf/grub/grub.cfg.ww``. Inspect the template to learn more about
the dracut booting process.
.. code-block:: shell
wwctl node set wwnode1 --tagadd GrubMenuEntry=dracut
.. note::
The ``GrubMenuEntry`` variable may be set at the node or profile level.
During boot, ``warewulfd`` will detect and dynamically serve an
initramfs from a node's container image in much the same way that it
can serve a kernel from a container image. This image is loaded by
iPXE (or GRUB) which directs dracut to fetch the node's container image
during boot.
The wwinit module provisions to tmpfs. By default, tmpfs is permitted
to use up to 50% of physical memory. This size limit may be adjustd
using the kernel argument `wwinit.tmpfs.size`. (This parameter is
passed to the `size` option during tmpfs mount. See ``tmpfs(5)`` for
more details.)
.. warning::
Kernel overrides are not currently fully supported during dracut initramfs boot.
Booting with GRUB
=================
@@ -214,3 +139,79 @@ is the following:
Warewulf delivers the initial `shim.efi` and `grub.efi` via http as taken
directly from the node's assigned container.
Booting with dracut
===================
Some systems, typically due to limitations in their BIOS or EFI
firmware, are unable to load container image of a certain size
directly with a traditional bootloader, either iPXE or GRUB. As a
workaround for such systems, Warewulf can be configured to load a
dracut initramfs from the container and to use that initramfs to load
the full container image.
Warewulf provides a dracut module to configure the dracut initramfs to
load the container image. This module is available in the
``warewulf-dracut`` subpackage, which must be installed in the
container image.
With the ``warewulf-dracut`` package installed, you can build an
initramfs inside the container.
.. code-block:: shell
dnf -y install warewulf-dracut
dracut --force --no-hostonly --add wwinit --kver $(ls /lib/modules | head -n1)
Set the node's iPXE template to ``dracut`` to direct iPXE to fetch the
node's initramfs image and boot with dracut semantics, rather than
booting the node image directly.
.. note::
Warewulf iPXE templates are located at ``/etc/warewulf/ipxe/`` when
Warewulf is installed via official packages. You can learn more
about how dracut booting works by inspecting its iPXE template at
``/etc/warewulf/ipxe/dracut.ipxe``.
.. code-block:: shell
wwctl node set wwnode1 --ipxe dracut
.. note::
The iPXE template may be set at the node or profile level.
Alternatively, to direct GRUB to fetch the node's initramfs image and boot with
dracut semantics, set a ``GrubMenuEntry`` tag for the node.
.. note::
Warewulf configures GRUB with a template located at
``/etc/warewulf/grub/grub.cfg.ww``. Inspect the template to learn more about
the dracut booting process.
.. code-block:: shell
wwctl node set wwnode1 --tagadd GrubMenuEntry=dracut
.. note::
The ``GrubMenuEntry`` variable may be set at the node or profile level.
During boot, ``warewulfd`` will detect and dynamically serve an
initramfs from a node's container image in much the same way that it
can serve a kernel from a container image. This image is loaded by
iPXE (or GRUB) which directs dracut to fetch the node's container image
during boot.
The wwinit module provisions to tmpfs. By default, tmpfs is permitted
to use up to 50% of physical memory. This size limit may be adjustd
using the kernel argument `wwinit.tmpfs.size`. (This parameter is
passed to the `size` option during tmpfs mount. See ``tmpfs(5)`` for
more details.)
.. warning::
Kernel overrides are not currently fully supported during dracut initramfs boot.