III. Boot managers
OS-BS is a FreeBSD boot manager. The main advantage of this boot manager is the size of its code, customizability and its price. It is a free software. It fits into MBR and does not require any additional partition to work. OS-BS can change active partitions on the fly. The choice of the desired operating system to boot is menu driven. Labels for operating systems and timeout are specified during OS-BS setup.
Ranish PM offers not only a boot manager but also partition management for free. There are even two boot managers: a compact one which fits into MBR, and an advanced one which requires some free space for its own partition. With those boot managers it is possible to boot operating systems from multiple hard disk drives. Ranish PM can hide and activate partitions on the fly. It can also change logical volumes to primary partition, which makes them boot-able.
Ranish PM is capable of creating most of known partitions including Solaris x86 and Linux partitions. It can format, clear, resize empty partitions, move and copy FAT-16 and FAT-32 partitions. It is possible to manually adjust partitioning data in MBR. The utility is able to recover MS DOS, Windows 9x, NT, W2K, PC DOS and DR DOS Volume Boot Code (partition boot block). Also manual changes to VBS of FAT-12, FAT-16 and FAT-32 are possible.
GRUB is an attempt to produce a bootloader for IBM PC-compatible machines that has both the capability to be friendly to beginning or otherwise non-technically interested users and the flexibility to help experts in diverse environments.
The GRUB project introduces Multiboot Standard proposal, which specifies general rules of behavior of boot processes used in operating systems. It is an attempt to cleanup and standardize PC boot methods.
Complexity is the price of rich functionality and convenience of GRUB. However, this complexity is hidden behind a simple text configuration file. GRUB requires additional space for executables and configuration files so, it does not fit the MBR. It offers menu driven, as well as, flexible command line user interface. The original feature of GRUB is geometry translation done independently of the BIOS and transparently for the operating system.
GRUB is free, distributed under GNU GPL license.
An axample entry in /grub/menu.lst to boot Solaris may look as follows:
title Solaris
rootnoverify (hd0,1)
chainloader +1
makeactive
boot
Of course, (hd0,1) should be modified according to the actual
partition scheme. In this example, hd0 mean the first hard disk
drive, and the number 1 means the second partition on that drive.
Hard disks, as well as partitions are counted from 0 in GRUB convention.
(hd0,4) specifies the first extended partition on the first hard
disk. Command makeactive tells GRUB to make the Solaris partition
active which is required to boot Solaris.
System Commander is a very sophisticated boot manager, which can boot all operating systems for IBM PC compatibles. It is a commercial software.
System Commander installs into MBR and requires FAT-16 partition to store its code and configuration data. It can change active partitions and hide partitions on the fly. Its OS Wizard prepares system for installation of a new operating system. Newly installed operating systems are automatically detected and included to the main menu. It is possible to setup users with different privileges for booting operating systems, so that the access to the machine is controlled by passwords.