Concepts Boot managers

[gogofe]

Hello,

I am looking into the topic of boot loaders but I have a few doubts that have come up. If you can correct me on the following statements:

1. If I understand correctly, a boot loader or OS loader is software that allows an OS to boot

2. Boot loaders are OS-dependent since I understand that to boot a Windows 8 as opposed to a Windows 95, the loader will have to look for certain file names to execute, load, and so on that will be different in name and location from one OS to another, right?

3. From what I have read, for each OS that you install on a partition, a boot loader would be installed in that partition. If I have an HDD with three primary partitions, if I install Windows XP on the 1st partition, a boot loader for XP would be installed in that partition, and if I install Linux on the 2nd partition, a Linux boot loader would be installed in this 2nd partition

4. Boot loaders are installed in the sector 0 of each of the partitions

5. The BIOS when it boots will read the sector 0 of the first partition to execute the boot loader located there

6. What does it mean when people say they have Windows 7 on one partition and then install XP on another and the latter overwrites the boot loader, does it mean that when installing XP, its boot loader instead of being written to the second partition would overwrite the boot loader of the first partition where Windows 7 is?

7. I understand that a boot loader that allows loading multiple OS, does it read a partition table to know which OS is on the different partitions or does it read from a file where the different OS are specified on the different partitions?

8. From the previous question when installing XP on the 1st partition and Windows 7 on the 2nd I have read that dual booting is allowed and the menu is displayed correctly but not the other way around, so how does the XP boot loader know that there is a Windows 7 installed on the second partition?

9. From the above, I understand that the XP boot loader not only allows booting XP but would allow booting other OS based on that this XP loader would load the boot loader of the selected OS, right?

Thanks!!

[Fassou]

In Boot sector - Wikipedia, the free encyclopedia they explain everything to you.

Salu2!

[gogofe]

Hello,

I don't quite understand English and I've read in Spanish but I can't resolve the doubts I mentioned to you.

Thank you

[Sylver]

6. What does it mean when people say they have Windows 7 on one partition and then install XP on another and the latter crashes the boot manager, does it mean that when installing XP, its boot manager instead of being written to the second partition would overwrite the boot manager of the first partition where Windows 7 is?

The first partition is the active one, from which the operating system always boots. If the files of the Active partition are not modified, the OS added later will not be detected, or there will be a conflict with the existing ones.

7. I understand that a boot manager that allows loading multiple OS, does it read a partition table to know which OS is on the different partitions or does it read from a file where the different OS on the different partitions are specified?

It reads the boot.ini, a file in which the partitions and the existing operating systems are included.

8. From the previous question, when installing an XP on the 1st partition and a Windows 7 on the 2nd, I have read that dual booting is allowed and the menu is displayed correctly but not the other way around, so how does the XP boot manager know that there is a Windows 7 installed on the second partition?

You have to tell it by modifying the relevant files.

9. From the above, I understand that the XP boot manager not only allows booting XP but would allow booting other OS based on that this XP manager would load the boot manager of the selected OS, right?

**
You have not explained yourself well, but according to what I have understood, no. The XP boot manager does not load other managers. On a computer, it loads the manager of the OS that is on the primary Active partition and only shows the OS that are listed in it.**

PD: Google a little more, there you will find good answers.

Regards

[cobito]

@gogofe:

2. Bootloaders are OS-dependent because I understand that to boot a Windows 8 as opposed to a Windows 95, the bootloader will have to look for certain file names to execute, load, and more that will be different in name and location from one OS to another, right?

As far as I remember, with Windows 95, 98, and Me there was no bootloader. The boot sector directly pointed to MS-DOS. With the NT era, things change. At least since Windows 2000, a bootloader has been implemented.

@gogofe:

3. According to what I've read, for each OS you install on a partition, a bootloader would be installed in that partition. If I have an HDD with three primary partitions, if I install Windows XP on the 1st partition, a bootloader for XP would be installed in that partition, and if I install Linux on the 2nd partition, a Linux bootloader would be installed in this 2nd partition

That's correct but you have to be careful about one thing: Windows bootloaders are a mess and only detect Windows partitions. If you install Linux and then Windows, the Windows installer will change the MBR (boot sector) to point to the Windows bootloader, which won't have detected Linux and you won't be able to boot Linux. If you install Windows first and then Linux, the Linux bootloader (generally called Grub or Lilo) will give you a choice between booting Linux or going to the Windows bootloader. If the Windows bootloader only has one operating system configured, it will boot Windows directly. If there are more than one Windows, once you've chosen to boot Windows from Grub or Lilo, you'll have to choose which version of Windows to boot.

@gogofe:

4. Bootloaders are installed in sectors 0 of each of the partitions

Incorrect. The MBR (or sector zero) is unique on a hard drive. The MBR will point to where the bootloader or the operating system is located. Bootloaders are installed in any sector of the partition like any other program.

@gogofe:

5. When booting, the BIOS will read sector 0 of the first partition to execute the bootloader located there

Incorrect. The system starts the bootloader that the MBR points to. Generally, it's the last bootloader that was installed.

@gogofe:

6. What does it mean when people say they have Windows 7 on one partition and then install XP on another and the latter trashes the bootloader, does it mean that when installing XP, its bootloader instead of writing to the second partition would trash the bootloader of the first partition where Windows 7 is?

I suppose people refer to the fact that the Windows XP installer is not able to detect Windows 7 and that when it rewrites the MBR to its bootloader, it only boots Windows XP. If Windows XP detected Windows 7 (I'm not sure now), even if it rewrote the MBR, both Windows XP and Windows 7 could be booted.

[gogofe]

Hello,

Thank you for the answers but I have a series of doubts. I have been reading on these websites:

*PC REPAIR CLINICS: System Boot: Boot Sector or Boot Record and on this *http://recursostic.educacion.es/observatorio/web/ca/software/software-general/534-el-gestor-de-arranque-gnu-grubaqui

Doubts:

1. Boot manager and loader are not the same, right? The boot manager is only one and is in the MBR and the loader is specific to each installed OS and is located in each of the partitions where there are OS installed

2. I understand that when the PC turns on after the POST, the BIOS executes if there is a boot manager that will be found in the MBR

3. If an OS has not been installed, there will be no boot manager in the MBR and the system will not be able to start and the BIOS will say that there is no system or something like that, right?

4. When an OS is installed, it houses a boot manager in the MBR but will it be a file or machine code?

6. The loaders are also not files but machine code that are in the partitions where there is an OS installed but this machine code will be helped by files from that partition, such as NTLDR to load OS like Win2000, WinXP….

7. When an OS is installed, it will install the boot manager of this OS in the MBR, no matter what partition it is.

Thanks!!

[Fassou]

This smells like homework ¬¬

[cobito]

gogofe, we are not going to do your homework for you, right?

[gogofe]

Hello,

I left school a long time ago. You can check it since I have messages from a long time ago in these forums.
It's just out of curiosity

Best regards

[cobito]

@gogofe:

Hola,

I left school a long time ago. You can check it since I have messages from quite a while ago in these forums.
It's just out of curiosity

Best regards

In that case, I have already given you the answers to your last question in my last post.

[Fassou]

Bootloader - Wikipedia, the free encyclopedia

Salu2!