Booting a Ramdisk or an ISO¶
Ironic supports booting a user provided ramdisk or an ISO image (starting with
the Victoria release) instead of deploying a node.
Most commonly this is performed when an instance is booted via PXE, iPXE or
Virtual Media, with the only local storage contents being those in memory.
It is suported by
ilo-virtual-media boot interfaces.
Ramdisk/ISO boot requires using the
ramdisk deploy interface. As with most
non-default interfaces, it must be enabled and set for a node to be utilized:
[DEFAULT] ... enabled_deploy_interfaces = direct,ramdisk ...
Once enabled and the conductor(s) have been restarted, the interface can be set upon creation of a new node:
baremetal node create --driver ipmi \ --deploy-interface ramdisk \ --boot-interface ipxe
or update an existing node:
baremetal node set <NODE> --deploy-interface ramdisk
You can also use it with redfish virtual media instead of iPXE.
Creating a ramdisk¶
A ramdisk can be created using the
ironic-ramdisk-base element from
ironic-python-agent-builder, e.g. with Debian:
export ELEMENTS_PATH=/opt/stack/ironic-python-agent-builder/dib disk-image-create -o /output/ramdisk \ debian-minimal ironic-ramdisk-base openssh-server dhcp-all-interfaces
You should consider using the following elements:
openssh-server to install the SSH server since it’s not provided by default by some minimal images.
The resulting files (
/output/ramdisk.initramfs in this case) can then be used when Booting a
Booting a ramdisk¶
Pass the kernel and ramdisk as normally, also providing the ramdisk as an image source, for example,
baremetal node set <NODE> \ --instance-info kernel=http://path/to/ramdisk.kernel \ --instance-info ramdisk=http://path/to/ramdisk.initramfs \ --instance-info image_source=http://path/to/ramdisk.initramfs baremetal node deploy <NODE>
The requirement to pass
image_source is artificial and will be fixed
in a future version of the Bare Metal service.
Booting an ISO¶
ramdisk deploy interface can also be used to boot an ISO image.
baremetal node set <NODE> \ --instance-info boot_iso=http://path/to/boot.iso baremetal node deploy <NODE>
This feature, when utilized with the
will only allow a kernel and ramdisk to be booted from the
supplied ISO file. Any additional contents, such as additional
ramdisk contents or installer package files will be unavailable
after the boot of the Operating System. Operators wishing to leverage
this functionality for actions such as OS installation should explore
use of the standard
deploy_interface along with the
instance_info/kernel_append_params setting to pass arbitrary
settings such as a mirror URL for the initial ramdisk to load data from.
This is a limitation of iPXE and the overall boot process of the
operating system where memory allocated by iPXE is released.
The intended use case is for advanced scientific and ephemeral workloads where the step of writing an image to the local storage is not required or desired. As such, this interface does come with several caveats:
Configuration drives are not supported with network boot, only with Redfish virtual media.
Disk image contents are not written to the bare metal node.
Users and Operators who intend to leverage this interface should expect to leverage a metadata service, custom ramdisk images, or the
instance_info/ramdisk_kernel_argumentsparameter to add options to the kernel boot command line.
When using PXE/iPXE boot, bare metal nodes must continue to have network access to PXE and iPXE network resources. This is contrary to most tenant networking enabled configurations where this access is restricted to the provisioning and cleaning networks
As with all deployment interfaces, automatic cleaning of the node will still occur with the contents of any local storage being wiped between deployments.