Typical Boot Sequence
– At power-on, the bootloader in an embedded system is first to get processor control.
– After the bootloader has performed some low-level hardware initialization, control is passed to the Linux kernel.
– Once the kernel has completed its own initialization, it must locate and mount a root filesystem
– Root filesystem will contain a set of initialization scripts.
Bootloader
– A piece of code that runs before any operating system is running
– Bootloader starts before any other software starts therefore it is highly processor specific and board specific.
– It performs the necessary initializations to prepare the system for the Operating system.
– Usually it starts from non-volatile storage.
U-Boot ( Universal Bootloader )
– U-Boot is an open source, primary boot loader used in embedded devices, developed in C.
– It is available for a number of different computer architectures : PPC, ARM, MIPS, AVR32, x86, 68k, Nios, MicroBlaze.
– It is a free Software: full source code under GPL.
– Configuration parameters and commands / command sequences (scripts !) can be stored in “environment variables”
which can be saved to non−volatile storage.
– For more information please refer http://www.denx.de/wiki/U-Boot/
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Techs it easy 