The boot interface manages booting of both the deploy ramdisk and the user instances on the bare metal node.
The PXE boot interface is generic and works with all hardware that supports booting from network. Alternatively, several vendors provide virtual media implementations of the boot interface. They work by pushing an ISO image to the node’s management controller, and do not require either PXE or iPXE. Check your driver documentation at Drivers, Hardware Types and Hardware Interfaces for details.
ipxe boot interfaces uses PXE or iPXE accordingly to
deliver the target kernel/ramdisk pair. PXE uses relatively slow and unreliable
TFTP protocol for transfer, while iPXE uses HTTP. The downside of iPXE is that
it’s less common, and usually requires bootstrapping using PXE first.
ipxe boot interfaces work by preparing a PXE/iPXE
environment for a node on the file system, then instructing the DHCP provider
(for example, the Networking service) to boot the node from it. See
Example: PXE Boot and Direct Deploy Process for a better understanding of the whole deployment
Both PXE and iPXE are configured differently, when UEFI boot is used instead of conventional BIOS boot. This is particularly important for CPU architectures that do not have BIOS support at all.
ipxe boot interface is used by default for many hardware types,
ipmi. Some hardware types, notably
their specific implementations of the PXE boot interface.
Additional configuration is required for this boot interface - see Configuring PXE and iPXE for details.
If you need to pass additional kernel parameters to the deployment/cleaning ramdisk (for example, to configure serial console), use the following configuration option:
[pxe] kernel_append_params = nofb vga=normal
The option was called
pxe_append_params before the Xena cycle.
Per-node and per-instance overrides are also possible, for example:
baremetal node set node-0 \ --driver-info kernel_append_params="nofb vga=normal" baremetal node set node-0 \ --instance-info kernel_append_params="nofb vga=normal"
Starting with the Zed cycle, you can combine the parameters from the
configuration and from the node using the special
baremetal node set node-0 \ --driver-info kernel_append_params="%default% console=ttyS0,115200n8"
Together with the configuration above, the following parameters will be appended to the kernel command line:
nofb vga=normal console=ttyS0,115200n8
Ironic does not do any de-duplication of the resulting kernel parameters. Both kernel itself and dracut seem to give priority to the last instance of the same parameter.
Previously our documentation listed the Linux kernel parameter
nomodeset as an option. This option is intended for troubleshooting,
and can greatly degrade performance with Matrox/Aspeed BMC Graphics
controllers which is very commonly used on physical servers. The
performance degredation can greatly reduce IO capacity upon every
console graphics update being written to the screen.
Enable persistent boot device for deploy/clean operation¶
For (i)PXE booting, Ironic uses non-persistent boot order changes for clean/deploy by default. For some drivers, persistent changes are far more costly than non-persisent ones, so this approach can bring a performance benefit.
In order to control this behavior, however, Ironic provides the
force_persistent_boot_device flag in the node’s
It allows the values
Default (make all changes but the last one
upon deployment non-persistent),
Always (make all changes persistent),
Never (make all boot order changes non-persistent). For example
in order to have only persistent changes one would need to set something
$ openstack baremetal node set --driver-info force_persistent_boot_device='Always' <node>
It is recommended to check if the node’s state has not changed as there is no way of locking the node between these commands.
The values ‘True’/’False’ for the option ‘force_persistent_boot_device’ in the node’s driver info for the (i)PXE drivers are deprecated and support for them may be removed in a future release. The former default value ‘False’ is replaced by the new value ‘Default’, the value ‘True’ is replaced by ‘Always’.