Common boot loaders

LILO (LInux LOader)

• A simple but flexible boot loader which can handle some other OSes too
• Given a set of kernel images listed in a config file, the lilo program stores a list of the disk sectors used by the image files and (if necessary) installs a boot sector which can read its second-stage loader
• The second-stage loader can select a kernel image and read it in using the map described above, or start another OS's boot loader in a specified partition's boot sector
• If not interrupted at boot time (by holding down a shift key) will load a default image, otherwise prompts for a boot selection
• Works well with typical PC BIOS implementations, but is also subject to their limits (like the 1024-cylinder limit in older BIOS disk access routines)
• You have to run lilo after installing a new kernel to make it bootable

GRUB

• On the surface, looks similar to LILO, in that it can boot a default kernel or allow selection of a kernel from a menu
• Also provides a more sophisticated command-line interface which can be used to change configuration parameters and select kernels at boot time, as well as just boot a default kernel if no input is given
• While its first-stage loader is still subject to BIOS limitations, the second-stage loader has its own disk-handling code and can also work with existing filesystems, allowing it to load kernel images specified by pathnames

BSD loader

• Probably the inspiration for GRUB; provides simple boot menu for kernel selection, plus command-line interface that can set configuration parameters and boot kernels specified by filesystem pathame

Boot monitor systems

• Common on vendor UNIX hardware (Sun, IBM, HP, etc.)
• Provide sophisticated command-line interfaces for setting system parameters, typically know enough about filesystems to boot kernels by pathname, some can also boot from network servers
• Usually tied to vendor hardware and filesystem layouts

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