Boot loader pdf

Note that these configurations snippets do not need to be the only configuration source for a boot loader. It may extend this list of entries with additional items from other configuration files for example its own native configuration files or automatically detected other entries without explicit configuration. Optionally it may sort the menu based on the machine-id and version fields, and possibly others. It uses the file name to identify specific items, for example in case it supports storing away default entry information somewhere.

A boot loader should generally not modify these files. The files created by a kernel package are private property of the kernel package and should be removed along with it.

This file is also private property of the kernel package and should be removed along with it. A UI application intended to show available boot options shall operate similar to a boot loader, but might apply additional filters, for example by filtering out the booted OS via the machine ID, or by suppressing all but the newest kernel versions.

It then installs an appropriate boot loader that can read these snippets. Finally, it installs one or more kernel packages. Currently, multiple Linux installations tend to fight over which boot loader becomes the primary one in possession of the MBR, and only that one installation can then update the boot loader configuration of it freely.

Other Linux installs have to be manually configured to never touch the MBR and instead install a chain-loaded boot loader in their own partition headers. Drop-in directories are otherwise now pretty ubiquitous on Linux as an easy way to extend configuration without having to edit, regenerate or manipulate configuration files.

For the sake of uniformity, we should do the same for extending the boot menu. Userspace code can sanely parse boot loader configuration which is essential with modern BIOSes which do not necessarily initialize USB keyboards anymore during boot, which makes boot menus hard to reach for the user. If userspace code can parse the boot loader configuration, too, this allows for UIs that can select a boot menu item to boot into, before rebooting the machine, thus not requiring interactivity during early boot.

To unify and thus simplify configuration of the various boot loaders around, which makes configuration of the boot loading process easier for users, administrators and developers alike. For boot loaders with configuration scripts such as grub2, adopting this spec allows for mostly static scripts that are generated only once at first installation, but then do not need to be updated anymore as that is done via drop-in files exclusively.

Why not simply rely on the EFI boot menu logic? Some firmware implementations do not offer a boot menu at all and instead unconditionally follow the EFI boot order, booting the first item that is working. If the firmware setup is used to reset all data usually all EFI boot entries are lost, making the system entirely unbootable, as the firmware setups generally do not offer a UI to define additional boot items. By placing the menu item information on disk, it is always available, regardless if the BIOS setup data is lost.

Harddisk images should be movable between machines and be bootable without requiring explicit EFI variables to be set. This also requires that the list of boot options is defined on disk, and not in EFI variables alone. It is thus useful if the OS UI has a standardized way to discover available boot options which can be booted to. The following keys are known: title shall contain a human readable title string for this menu item.

This will be displayed in the boot menu for the item. This name should be descriptive and does not have to be unique. If a boot loader discovers two entries with the same title it is a good idea to show more than just the raw title in the UI, for example by appending the version field. This field is optional. This is usually the kernel version and is intended for use by OSes to install multiple kernel versions at the same time with the same title field. This field shall be in a syntax that is useful for Debian-style version sorts, so that the boot loader UI can determine the newest version easily and show it first or preselect it automatically.

Example: 3. This is useful for boot loaders and applications to filter out boot entries, for example to show only a single newest kernel per OS, or to group items by OS, or to maybe filter out the currently booted OS in UIs that want to show only other installed operating systems. This ID shall be formatted as 32 lower case hexadecimal characters i. This key is optional. Example: b3fd74c13b1f04ccfbae8. Mx6 platform.

Presenter: Sean Hudson, Mentor Graphics, Inc Summary: In continuation to last year's talk, this presentation provides an update on the current status of the shared logging feature between the boot-loader U-boot and kernel. Presenter: David Brown, Linaro, Ltd Summary: In this presentation, the presenter reviews the current status of the MCUboot project and covers the work being done to support multiple image update. Presenter: John Ogness Summary: This session discusses about methods to make Linux itself as a bootloader and faster and reliable ways to boot it.

Presenter: Lukasz Majewski Summary: The presentation talks present status and future plans for device upgrade procedures on U-Boot. Presenter: Sascha Hauer, Pengutronix e. Summary: This presentation takes a tour through Barebox bootloader. From eLinux. Jump to: navigation , search.