jcs.org
"Das U-Boot" Source Tree
1.. SPDX-License-Identifier: GPL-2.0+:
2
3Extlinux Bootmeth
4=================
5
6`Extlinux <https://uapi-group.org/specifications/specs/boot_loader_specification>`_
7(sometimes called syslinux) allows U-Boot to provide a menu of available
8operating systems from which the user can choose.
9
10U-Boot includes a parser for the `extlinux.conf` file. It consists primarily of
11a list of named operating systems along with the kernel, initial ramdisk and
12other settings. The file is stored in the `extlinux/` subdirectory, possibly
13under the `boot/` subdirectory. This list of prefixes (``{"/", "/boot"}`` by
14default) can be selected with the `filename-prefixes` property in the bootstd
15device.
16
17Note that the :doc:`pxelinux` uses the same file format, but in a
18network context.
19
20When invoked on a bootdev, this bootmeth searches for the file and creates a
21bootflow if found.
22
23When the bootflow is booted, the bootmeth calls ``pxe_setup_ctx()`` to set up
24the context, then ``pxe_process()`` to process the file. Depending on the
25contents, this may boot an operating system or provide a list of options to
26the user, perhaps with a timeout.
27
28The compatible string "u-boot,extlinux" is used for the driver. It is present
29if `CONFIG_BOOTMETH_EXTLINUX` is enabled.