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