| Simon Glass | 08379df | 2024-07-17 09:30:55 +0100 | [diff] [blame] | 1 | .. SPDX-License-Identifier: GPL-2.0+: |
| 2 | |
| 3 | PXE Bootmeth |
| 4 | ============ |
| 5 | |
| 6 | PXE (Preboot eXecution-Environment) provides a way to boot an operating system |
| 7 | over a network interface. The PXE bootmeth supports PXELINUX and allows U-Boot to |
| 8 | provide a menu of possible Operating Systems from which the user can choose. |
| 9 | |
| 10 | U-Boot includes a parser for the `extlinux.conf` file described |
| 11 | `here <https://uapi-group.org/specifications/specs/boot_loader_specification>`_. |
| 12 | It consists primarily of a list of named operating systems along with the |
| 13 | kernel, initial ramdisk and other settings. The file is retrieved from a network |
| 14 | server using the TFTP protocol. |
| 15 | |
| 16 | When invoked on a bootdev, this bootmeth searches for the file and creates a |
| 17 | bootflow if found. See |
| 18 | `PXELINUX <https://wiki.syslinux.org/wiki/index.php?title=PXELINUX>`_ for |
| 19 | a full description of the search procedure. |
| 20 | |
| 21 | When the bootflow is booted, the bootmeth calls ``pxe_setup_ctx()`` to set up |
| 22 | the context, then ``pxe_process()`` to process the file. Depending on the |
| 23 | contents, this may boot an Operating System or provide a list of options to the |
| 24 | user, perhaps with a timeout. |
| 25 | |
| 26 | The compatible string "u-boot,extlinux-pxe" is used for the driver. It is |
| 27 | present if `CONFIG_BOOTMETH_EXTLINUX_PXE` is enabled. |