Das U-Boot
Encyclopedia
Das U-Boot is an open source
, primary boot loader used in embedded devices
. It is available for a number of different computer architecture
s, including PPC
, ARM
, MIPS
, AVR32
, x86
, 68k
, Nios
, and MicroBlaze
.
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 name comes from the abbreviated form of Das Unterseeboot, German for "the 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."
Open source
The term open source describes practices in production and development that promote access to the end product's source materials. Some consider open source a philosophy, others consider it a pragmatic methodology...
, primary boot loader used in embedded devices
Embedded system
An embedded system is a computer system designed for specific control functions within a larger system. often with real-time computing constraints. It is embedded as part of a complete device often including hardware and mechanical parts. By contrast, a general-purpose computer, such as a personal...
. It is available for a number of different computer architecture
Computer architecture
In computer science and engineering, computer architecture is the practical art of selecting and interconnecting hardware components to create computers that meet functional, performance and cost goals and the formal modelling of those systems....
s, including PPC
PowerPC
PowerPC is a RISC architecture created by the 1991 Apple–IBM–Motorola alliance, known as AIM...
, ARM
ARM architecture
ARM is a 32-bit reduced instruction set computer instruction set architecture developed by ARM Holdings. It was named the Advanced RISC Machine, and before that, the Acorn RISC Machine. The ARM architecture is the most widely used 32-bit ISA in numbers produced...
, MIPS
MIPS architecture
MIPS is a reduced instruction set computer instruction set architecture developed by MIPS Technologies . The early MIPS architectures were 32-bit, and later versions were 64-bit...
, AVR32
AVR32
The AVR32 is a 32-bit RISC microprocessor architecture designed by Atmel. The microprocessor architecture was designed by a handful of people educated at the Norwegian University of Science and Technology, including lead designer Øyvind Strøm, PhD and CPU architect Erik Renno, M.Sc in Atmel's...
, x86
X86 architecture
The term x86 refers to a family of instruction set architectures based on the Intel 8086 CPU. The 8086 was launched in 1978 as a fully 16-bit extension of Intel's 8-bit based 8080 microprocessor and also introduced segmentation to overcome the 16-bit addressing barrier of such designs...
, 68k
68k
The Motorola 680x0/m68000/68000 is a family of 32-bit CISC microprocessors. During the 1980s and early 1990s, they were popular in personal computers and workstations and were the primary competitors of Intel's x86 microprocessors...
, Nios
Nios embedded processor
Nios was Altera's first configurable 16-bit embedded processor for its FPGA product-line. For new designs, Altera recommends the 32-bit Nios II. It is now considered obsolete.- See also :* LatticeMico8* LatticeMico32* MicroBlaze* PicoBlaze* Micon P200...
, and MicroBlaze
MicroBlaze
The MicroBlaze is a soft processor core designed for Xilinx FPGAs from Xilinx. As a soft-core processor, MicroBlaze is implemented entirely in the general-purpose memory and logic fabric of Xilinx FPGAs.-Overview:...
.
Supported File Systems
- CramfsCramfsThe compressed ROM file system is a free read-only Linux file system designed for simplicity and space-efficiency. It is mainly used in embedded systems and small-footprint systems....
- ext2Ext2The ext2 or second extended filesystem is a file system for the Linux kernel. It was initially designed by Rémy Card as a replacement for the extended file system ....
- FATFile Allocation TableFile Allocation Table is a computer file system architecture now widely used on many computer systems and most memory cards, such as those used with digital cameras. FAT file systems are commonly found on floppy disks, flash memory cards, digital cameras, and many other portable devices because of...
- FDOS
- JFFS2JFFS2Journalling Flash File System version 2 or JFFS2 is a log-structured file system for use with flash memory devices. It is the successor to JFFS. JFFS2 has been included in the Linux kernel since the 2.4.10 release. JFFS2 is also available for a couple of bootloaders like Das U-Boot, Open...
- ReiserFSReiserFSReiserFS is a general-purpose, journaled computer file system designed and implemented by a team at Namesys led by Hans Reiser. ReiserFS is currently supported on Linux . Introduced in version 2.4.1 of the Linux kernel, it was the first journaling file system to be included in the standard kernel...
- UBIFSUBIFSThe Unsorted Block Image File System is a successor to JFFS2, and competitor to LogFS, as a file system for use with raw flash memory media. Development began in earnest in 2007, with the first stable release made to Linux kernel 2.6.27 in October 2008.Note that UBIFS works on top of an Unsorted...
- YAFFS2
History
The project began in October 1999 as PPCBoot. It originally started in work done by Magnus Damm on a 8xx PowerPC bootloader called 8xxROM. When Wolfgang Denk moved the project to SourceForge.net, the project was renamed 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
Fork (software development)
In software engineering, a project fork happens when developers take a legal copy of source code from one software package and start independent development on it, creating a distinct piece of software...
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
MicroBlaze
The MicroBlaze is a soft processor core designed for Xilinx FPGAs from Xilinx. As a soft-core processor, MicroBlaze is implemented entirely in the general-purpose memory and logic fabric of Xilinx FPGAs.-Overview:...
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 name comes from the abbreviated form of Das Unterseeboot, German for "the submarine." It is free software
Free software
Free software, software libre or libre software is software that can be used, studied, and modified without restriction, and which can be copied and redistributed in modified or unmodified form either without restriction, or with restrictions that only ensure that further recipients can also do...
released under the terms of the GNU General Public License
GNU General Public License
The GNU General Public License is the most widely used free software license, originally written by Richard Stallman for the GNU Project....
. It can be built on an x86 PC for any supported architecture using a cross development GNU toolchain
Programming tool
A programming tool or software development tool is a program or application that software developers use to create, debug, maintain, or otherwise support other programs and applications...
, 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."