The booting process consists of loading the kernel and other necessary parts of the operating system into the computer's main memory from some storage device. This storage device is usually the built-in hard disk drive (HDD), but it can also be removable media such as a CDROM, floppy disk or USB key memory stick. The kernel is the core of the operating system, and it remains in memory for the duration of the time that the computer is in operation.
The term bootable is also used to refer to any removable storage device or any software that contains sufficient components of an operating system and other necessary utilities (e.g., for file decompression) such that it can be loaded into a computer's main memory and allow the computer to start up.
Perhaps the best known example of a bootable CDROM is the Knoppix liveCD. Knoppix is a distribution (i.e., version) of Linux that is based on the highly regarded Debian distribution. A liveCD allows any computer with a CD (compact disk) drive (or to which an external CD drive can be connected) and an appropriate processor to be converted almost immediately, but temporarily, into a computer having the same operating system as contained on the CDROM without installing having to anything on the computer's HDD. Thus, the Knoppix liveCD allows virtually any computer with an x86 (i.e., Intel-compatible) processor to be converted almost immediately into a Linux computer.
Bootable CDROMs conform to the El Torito bootable CD specification, which is an extension to the ISO 9660, the standard CDROM specification. El Torito was first released in January 1995 as a joint proposal by IBM and Phoenix Technologies, a manufacturer of BIOSs (basic input output systems).
muLinux is a miniaturized distribution of Linux that is designed to fit on a single 1.44MB floppy disk and serve as a live floppy. That is, it can be used to boot and operate on any x86 computer that has a floppy disk drive (or to which an external floppy drive can be connected). Another operating system that is well suited for making into a bootable floppy is FreeDOS, which is a free clone of MS-DOS.
vmlinuz is the bootable, compressed Linux kernel executable. An executable, also called an executable file, is the ready-to-run form of a program. Unlike conventional executable files, however, vmlinuz does not require for an operating system to already be in memory in order for it to run, as it loads itself into memory at an early stage of the boot process.
Created December 27, 2005.