93e57fd727
When pre-built images are used, they can be quite large (CoreOS is more than 700 MiB, the same probably applies to other live ISOs). When deploying many nodes at the same time, the disk usage may become really large. This change uses the same ImageCache as for instance images for ISO images as well. Story: #2008909 Task: #42497 Change-Id: I891fd484f98042039895d82046199e8b29975100
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6.1 KiB
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163 lines
6.1 KiB
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Booting a Ramdisk or an ISO
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===========================
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Ironic supports booting a user provided ramdisk or an ISO image (starting with
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the Victoria release) instead of deploying a node.
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Most commonly this is performed when an instance is booted via PXE, iPXE or
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Virtual Media, with the only local storage contents being those in memory.
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It is suported by ``pxe``, ``ipxe``, ``redfish-virtual-media`` and
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``ilo-virtual-media`` boot interfaces.
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Configuration
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-------------
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Ramdisk/ISO boot requires using the ``ramdisk`` deploy interface. As with most
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non-default interfaces, it must be enabled and set for a node to be utilized:
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.. code-block:: ini
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[DEFAULT]
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...
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enabled_deploy_interfaces = direct,ramdisk
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...
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Once enabled and the conductor(s) have been restarted, the interface can
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be set upon creation of a new node:
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.. code-block:: shell
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baremetal node create --driver ipmi \
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--deploy-interface ramdisk \
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--boot-interface ipxe
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or update an existing node:
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.. code-block:: shell
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baremetal node set <NODE> --deploy-interface ramdisk
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You can also use it with :ref:`redfish virtual media
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<redfish-virtual-media-ramdisk>` instead of iPXE.
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Creating a ramdisk
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------------------
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A ramdisk can be created using the ``ironic-ramdisk-base`` element from
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ironic-python-agent-builder_, e.g. with Debian:
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.. code-block:: shell
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export ELEMENTS_PATH=/opt/stack/ironic-python-agent-builder/dib
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disk-image-create -o /output/ramdisk \
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debian-minimal ironic-ramdisk-base openssh-server dhcp-all-interfaces
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You should consider using the following elements:
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* openssh-server_ to install the SSH server since it's not provided by default
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by some minimal images.
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* devuser_ or dynamic-login_ to provide SSH access.
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* dhcp-all-interfaces_ or simple-init_ to configure networking.
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The resulting files (``/output/ramdisk.kernel`` and
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``/output/ramdisk.initramfs`` in this case) can then be used when `Booting a
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ramdisk`_.
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Booting a ramdisk
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-----------------
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Pass the kernel and ramdisk as normally, also providing the ramdisk as an image
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source, for example,
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.. code-block:: shell
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baremetal node set <NODE> \
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--instance-info kernel=http://path/to/ramdisk.kernel \
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--instance-info ramdisk=http://path/to/ramdisk.initramfs
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baremetal node deploy <NODE>
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.. note::
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Before the Xena release, the ``image_source`` field was also required::
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--instance-info image_source=http://path/to/ramdisk.initramfs
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Booting an ISO
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--------------
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The ``ramdisk`` deploy interface can also be used to boot an ISO image.
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For example,
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.. code-block:: shell
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baremetal node set <NODE> \
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--instance-info boot_iso=http://path/to/boot.iso
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baremetal node deploy <NODE>
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.. warning::
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This feature, when utilized with the ``ipxe`` ``boot_interface``,
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will only allow a kernel and ramdisk to be booted from the
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supplied ISO file. Any additional contents, such as additional
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ramdisk contents or installer package files will be unavailable
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after the boot of the Operating System. Operators wishing to leverage
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this functionality for actions such as OS installation should explore
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use of the standard ``ramdisk`` ``deploy_interface`` along with the
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``instance_info/kernel_append_params`` setting to pass arbitrary
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settings such as a mirror URL for the initial ramdisk to load data from.
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This is a limitation of iPXE and the overall boot process of the
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operating system where memory allocated by iPXE is released.
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By default the Bare Metal service will cache the ISO locally and serve from its
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HTTP server. If you want to avoid that, set the following:
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.. code-block:: shell
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baremetal node set <NODE> \
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--instance-info ramdisk_image_download_source=http
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ISO images are also cached across deployments, similarly to how it is done for
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normal instance images. The URL together with the last modified response header
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are used to determine if an image needs updating.
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Limitations
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-----------
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The intended use case is for advanced scientific and ephemeral workloads
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where the step of writing an image to the local storage is not required
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or desired. As such, this interface does come with several caveats:
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* Configuration drives are not supported with network boot, only with Redfish
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virtual media.
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* Disk image contents are not written to the bare metal node.
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* Users and Operators who intend to leverage this interface should
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expect to leverage a metadata service, custom ramdisk images, or the
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``instance_info/ramdisk_kernel_arguments`` parameter to add options to
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the kernel boot command line.
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* When using PXE/iPXE boot, bare metal nodes must continue to have network
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access to PXE and iPXE network resources. This is contrary to most tenant
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networking enabled configurations where this access is restricted to
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the provisioning and cleaning networks
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* As with all deployment interfaces, automatic cleaning of the node will
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still occur with the contents of any local storage being wiped between
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deployments.
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Common options
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--------------
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Disable persistent boot device for ramdisk iso boot
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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For iso boot, Ironic sets the boot target to continuously boot from
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the iso attached over virtual media. This behaviour may not always be
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desired e.g. if the vmedia is installing to hard drive and then
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rebooting. In order to instead set the virtual media to be one time
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boot Ironic provides the ``force_persistent_boot_device`` flag in the
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node's ``driver_info``. Which can be set to ``Never``::
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$ openstack baremetal node set --driver-info force_persistent_boot_device='Never' <node>
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.. _ironic-python-agent-builder: https://opendev.org/openstack/ironic-python-agent-builder
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.. _openssh-server: https://docs.openstack.org/diskimage-builder/latest/elements/openssh-server/README.html
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.. _devuser: https://docs.openstack.org/diskimage-builder/latest/elements/devuser/README.html
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.. _dynamic-login: https://docs.openstack.org/diskimage-builder/latest/elements/dynamic-login/README.html
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.. _dhcp-all-interfaces: https://docs.openstack.org/diskimage-builder/latest/elements/dhcp-all-interfaces/README.html
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.. _simple-init: https://docs.openstack.org/diskimage-builder/latest/elements/simple-init/README.html
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