Linux bootloader.
What is a bootloader?
In computing, booting or booting-up, is the process that starts an operating system when a computer system is turned on. A boot sequence is then followed, step by step, running some initial tests of the hardware and then initializing the bootloader.
A bootloader loads the operating system, often from a list of options, selecting the default option if another is not selected by the user within a set period of time. The user interface one sees can be a simply text display or a graphical user interface.
When a computer starts-up, the BIOS is loaded. The master boot record (MBR) is accessed from the first sector on the boot-able media. The MBR is limited to a single operating system, i.e. one distribution on Linux (Ubuntu, OpenSuse, etc.). The MBR is split up into two parts, part or all of the boot loader and information on the drive partitions. The BIOS locates and loads the first part of the bootloader, known as the initial program loader or IPL. The IPL checks the partition table to locate the second stage of the bootloader and load it.
The second part of the bootloader is much larger than the first, which is limited by the size of files the BIOS can access. The second part is also the part that is visible, so often people think it is the only part of the bootloader. This part contains the user interface to display the bootloader to the user and kernels to help the computer function correctly in the initial stages.
With newer Linux bootloaders, you have new options like the ability to load from a list of operating systems, use encrypted passwords and so on. This allows the flexibility to have a number of different operating systems installed on separate drives or separate partitions on the same drive. Different popular distributions of Linux, like Ubuntu Linux and OpenSuse Linux, as well as Microsoft Windows operating systems, can coexist happily together. This gives the user ultimate flexibility at boot time.
Two of the more popular bootloaders on Linux operating systems are LILO and GRUB.
Linux Loader
Linux Loader, or LILO, is the most common bootloader for Linux. It has been around many years, enjoys rich support from the Linux community and continues to evolve with new features added over time. There are many features to help troubleshoot a system having problems booting-up successfully. It also permits dual boot of a Linux distribution with any other operating system.
LILO is file system agnostic that allow to boot the OS from a floppy disc, CD-Rom, DVD, USB pen drive or hard drive. LILO is also flexible enough to be loaded from master boot record or boot sector of harddisk partiton. If you want to load LILO from boot sector then you must set up something in the master boot record in order to call the LILO that place on the harddisk partition.
GRUB
GNU GRUB, or GRUB, is fast becoming the boot loader of choice for many Linux users. The growing popularity of the Ubuntu Linux distribution that uses GRUB as standard is one reason for this, with approximately one third of Linux users using Ubuntu.
GRUB can also install on a range of media – floppy disc, CD-Rom, DVD, USB pen drive and hard drive – but it beats out LILO because the number of boot selections are unlimited. Given enough media options, this allows an enthusiast or Linux technician to load the latest stable release for one distribution of Linux, as well as a number of beta versions and special configurations for testing purposes, without the concern of running out of boot selections.
GRUB is also network ready and comes with an attractive graphical user interface.
Thank you,
Jitkasem Pintaya
