What is a Boot Sequence?

Question

What is a Boot Sequence?

Answer 1

In computing, booting (booting up) is a bootstrapping process that starts operating systems when the user turns on a computer system.



In BIOS boot sequence menu we have to set the order of the devices according to which our computer boots.



Ex: If you keep CDROM as the first boot device in your BIOS settings, the computer will search for a bootable CD in the cd drive, if it is there it will boot from it, otherwise it will search for the bootable media in the second option you kept in the boot seuence (usually a harddisk).

Answer 2

When you hit the power button on your computer a whole lot of stuff happens. We call this the boot process. In the days when I first started using computers there was literally a "boot disk", a floppy (5.25" not a 3.5") disk that told the system where to go and what to do so that the operating system would start up. Since then the boot sequence has become somewhat more complicated. So let me take you thru the steps the computer takes to get started. For my example I'm going to use a Windows XP system.



1. First is the POST, this stands for Power On Self Test, for the computer. This process tests memory as well as a number of other subsystems. You can usually monitor this as it runs each test. After that is complete the system will run POST for any device that has a BIOS (Basic Input-Output System). An AGP has its own BIOS, as do some network cards and various other devices.

2. Once the POST is complete and the BIOS is sure that everything is working properly, the BIOS will then attempt to read the MBR (Master Boot Record). This is the first sector of the first hard drive (called the Master or HD0). When the MBR takes over it means that Windows is now in control.

3. The MBR looks at the BOOT SECTOR (the first sector of the active partition). That is where NTLDR is located, NTLDR is the BOOT LOADER for Windows XP. NTLDR will allow memory addressing, initiate the file system, read the boot.ini and load the boot menu. NTLDR has to be in the root of the active partition as do NTDETECT.COM, BOOT.INI, BOOTSECT.DOS (for multi-OS booting) and NTBOOTDD.SYS (if you have SCSI adapters)

4. Once XP is selected from the Boot Menu, NTLDR will run NTDETECT.COM, BOOT.INI and BOOTSECT.DOS to get the proper OS selected and loaded. The system starts in 16-bit real mode and then moves into 32-bit protected mode.

5. NTLDR will then load NTOSKRNL.EXE and HAL.DLL. Effectively, these two files are windows XP. They must be located in %SystemRoot%System32.

6. NTLDR reads the registry, chooses a hardware profile and authorizes device drivers, in that exact order.

7. At this point NTOSKRNL.EXE takes over. It starts WINLOGON.EXE that in turn starts LSASS.EXE, this is the program that display the Logon screen so that you can logon.



I hope this helps :)

Answer 3

a boot sequence is the initial set of operations that the computer performs when it is switched on.

Answer 4

boot Sequence series of commands ran by your computer to boot your operating system when you turn on your computer

Answer 5

In layman's terms, it's the order in which your computer will access drives from which it will attempt to boot. For example, your computer might attempt to boot from your optical drive, then your USB ports, then your network, and finally your hard drive, which is where your operating system is usually installed.