|Developer(s)||DENX Software Engineering|
|Initial release||October 15, 1999|
|Stable release||v2013.07 / July 22, 2013|
|License||GNU GPLv2 and GNU GPLv2+|
Das U-Boot (Universal Bootloader) is an open source, primary boot loader used in embedded devices. It is available for a number of different computer architectures, including PPC, ARM, MIPS, AVR32, x86, 68k, Nios, and MicroBlaze.
Supported File Systems
Device tree is a data structure for describing hardware layout. Using Device tree, a vendor might be able to use an unmodified mainline Das U-Boot on otherwise special purpose hardware. As also adopted by the Linux kernel, Device tree is intended to ameliorate the situation in the embedded industry, where a vast number of product specific forks (of Das U-Boot and Linux) exist. The ability to run mainline software practically gives customers indemnity against lack of vendor updates.
The project's origin is a 8xx PowerPC bootloader called 8xxROM written by Magnus Damm. In October 1999 Wolfgang Denk moved the project to SourceForge.net and renamed it to PPCBoot, because SF.net did not allow project names starting with digits. Version 0.4.1 of PPCBoot was first publicly released July 19, 2000.
In 2002 a previous version of the source code was briefly forked into a product called ARMBoot, but was merged back into the PPCBoot project shortly thereafter. In November 2002 PPCBoot−2.0.0 was released. This marked the last release under the PPCBoot name, as it was renamed to reflect its support of the ARM architecture in addition to the PPC ISA.
PPCBoot−2.0.0 became U−Boot−0.1.0 in November 2002, with support added for x86 processor architecture. Additional architecture support was added in the following months: MIPS32 in March 2003, MIPS64 in April, Altera NIOS−32 in October, Coldfire in December, and Microblaze in April 2004. The May 2004 release of U-Boot-1.1.2 included support for 216 different board manufacturers across the various architectures. 
The current name Das U-Boot adds a German definite article, to create a bilingual pun on the German word for "submarine." It is free software released under the terms of the GNU General Public License. It can be built on an x86 PC for any supported architecture using a cross development GNU toolchain, for example crosstool, the Embedded Linux Development Kit (ELDK) or OSELAS.Toolchain.
The importance of Das U-Boot in embedded Linux systems is quite succinctly stated in the book Building Embedded Linux Systems, by Karim Yaghmour, whose text about U-Boot begins, "Though there are quite a few other bootloaders, 'Das U-Boot,' the universal bootloader, is arguably the richest, most flexible, and most actively developed open source bootloader available."
- PPCBoot Homepage: Authors
- "U-Bootdoc History". Retrieved Sept 4, 2011.
- Building Embedded Linux Systems by Kareem Yaghmour, Chapter 9