260px-GRUB_screenshotBy Eddison Sherry

Booting (booting up) in computing is the process of starting the Operating System when the computer is switched on. A boot sequence is the initial set of operations performed when the computer is switched on. Some commonly used bootloaders are GRUB, BOOTMGR, Syslinux, LILO, NTLDR. Linux booting process is much simple to understand and much things to learn.

300px-LiloFor Linux, the most common boot loaders are LILO(LInux Loader), LOADLIN (LOAD LINux) and GRUB (GRand Unified Bootloader). LILO is the most popular boot loader for those users who employ Linux as the main, or only, operating system.LILO is a very fast bootloader. LOADLIN is used by those who have multiple operating systems. LOADLIN is sometimes used as a backup boot loader for Linux in case LILO fails. GRUB is preferred by many users of Red Hat Linux.

A boot loader consists of three programs:

The boot sector program (512 bytes) is directly loaded by the BIOS at boot time.

The second stage program is loaded by the boot sector program and it can do everything you program it for.

The boot loader installer is used to install the boot loader and the second stage program onto the boot disk. These have to be stored in special locations, into the first sector of boot device. So they cannot be copied with a mere copy command.

Now we will compare the features of mostly used GRUB and LILO bootloaders.GRUB is capable of loading a variety of free and proprietary operating systems. GRUB will work well with Linux, DOS, Windows, or BSD. GRUB is dynamically configurable which means changes can be made during the boot time, which includes altering existing boot entries, adding custom entries, selecting different kernels, or modifying initrd. GRUB supports Logical Block Address mode meaning if the computer has a modern BIOS which can access more than 8GB (first 1024 cylinders) of hard disk space, GRUB will automatically be able to access it. Besides these GRUB can be run from or be installed to any device like floppy disk, hard disk, CD-ROM, USB drive, network drive and can load operating systems from just as many locations, including network drives. It can also decompress operating system images before booting them.

LILO is a sensible option for many Linux users and is a fast bootloader. LILO does not depend on a particular file system.One of up to sixteen different images can be selected at boot time. Parameters can be set independently for each kernel. LILO can be placed either in the master boot record (MBR) or the boot sector of a partition. At system start, only the BIOS drivers are available for LILO to access hard disks. So with very old BIOS, the accessible area is limited to cylinders 0 to 1023 of the first two hard disks. For later BIOS, LILO can use 32-bit logical block addressing (LBA) to access all the hard disks that the BIOS allows. LILO has some disadvantages when compared with GNU GRUB.

LILO supports only up to 16 different boot selections; GRUB supports an unlimited number of boot entries.

LILO cannot boot from network.

LILO must be written again every time you change the configuration file; GRUB does not.

LILO does not have an interactive command interface.

Finally, there are multiple choices of bootloaders which work with the Linux operating system of which the user can choose the ones best suited for the requirements.

Eddison Sherry had been working in Linux and other Unix flavours for long years. He had been writing blogs and article on the Linux Storage, Linux Commands and Linux Server Administration. If you are working on Linux or Unix Server its best to have a look on his blogs at Linux Technical Forum.

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Multi boot or Multi booting (usually dual booting, but many OSes can be booted from the same computer) is the act of installing multiple operating systems on a computer, and being able to choose which one to boot when switching on the computer power. The program which makes multi booting possible is called a boot loader.grub_with_ubuntu_and_windows_vista1

Multi booting is useful in many situations, such as those where several pieces of software require different operating systems and cannot be run on a single system. A multi boot configuration will allow a user to use all of this software on one computer. Another reason for setting up a multi boot system can be that one wants to investigate or test a new operating system without switching completely. Multi booting allows one to get to know the new system, configure all applications needed and migrate data before making the final step and removing the old operating system. This is often accomplished by using a boot loader that can boot more than one operating system, such as NTLDR, LILO, or GRUB.

Multi booting can also aid software developers where multiple operating systems are required for development or testing purposes. Having these systems on one machine can greatly reduce hardware costs. (However hardware costs are counterbalanced by system management costs, and the costs of the unavailability of the software that cannot be run at any given moment. Another solution to these problems is to use virtual machine software to emulate another computer from within the operating system of choice.)

A popular multi-boot configuration is a mixed-OS system in which Linux is one of the secondary (or primary) installations. In terms of business strategy, Windows does not facilitate or support multi-boot systems, other than allowing for partition-specific installations, and no choice of boot loader is offered. To deal with such installs requires consultation with Linux afficionados and techs, who are typically well-versed in the concept.

The basic concept involves partitioning a disk, to accommodate each planned installation, including separate partitions for data storage or backups. The partitions should be done with a Windows partitioning tool (diskpart, Disk Management), rather than a Linux tool (parted, QTparted), for the simple reason that Windows is more particular (cf. “picky”) about how the partition table is written and will occasionally complain or even show errors if its installed to a Linux-created (or sometimes modified) partition table. Linux tools are powerful, (ie. shrinking an NTFS drive) but Windows has particularities which must be considered. (See master boot record and extended boot record).

Windows should be installed to the first primary drive. Though Windows can be installed to another drive, certain particularities (drive letter assignments, expected system partition number) can make such installations problematic, while Linux installations on primary or logical drives have no such problems whatsoever.

The boot manager/loader should be installed by the Linux distribution. All Windows installations will be easily found by Linux, but Windows boot managers do not find Linux installations (nor does Windows deal natively with Linux file systems).

Get Linux Today!

Excellent resources below:

How to dual boot Windows XP and Linux (XP installed first) — the step-by-step guide with screenshots

Illustrated Dual Boot Site – Awesome site with all things Linux!

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