In a dual boot system, how does the BIOS choose which bootloader to run?
I have a dual boot of Windows and Ubuntu. When I switch on the machine, the BIOS does POST and after that the bootloader starts.
I want to understand how the BIOS chooses which bootloader to run. I want to know the process going on between the BIOS and the bootloader in a dual boot computer.
boot bootloader bios
edited Nov 29 '17 at 19:43
karel
56.8k11126146
asked Nov 29 '17 at 9:58
Prashant Singh
10318
add a comment |
I have a dual boot of Windows and Ubuntu. When I switch on the machine, the BIOS does POST and after that the bootloader starts.
I want to understand how the BIOS chooses which bootloader to run. I want to know the process going on between the BIOS and the bootloader in a dual boot computer.
boot bootloader bios
edited Nov 29 '17 at 19:43
karel
56.8k11126146
asked Nov 29 '17 at 9:58
Prashant Singh
10318
6
I suggest you read en.wikipedia.org/wiki/Power-on_self-test , en.wikipedia.org/wiki/BIOS , en.wikipedia.org/wiki/Master_boot_record , en.wikipedia.org/wiki/GUID_Partition_Table , en.wikipedia.org/wiki/UEFI .
– waltinator
Nov 29 '17 at 14:00
add a comment |
I have a dual boot of Windows and Ubuntu. When I switch on the machine, the BIOS does POST and after that the bootloader starts.
I want to understand how the BIOS chooses which bootloader to run. I want to know the process going on between the BIOS and the bootloader in a dual boot computer.
boot bootloader bios
edited Nov 29 '17 at 19:43
karel
56.8k11126146
asked Nov 29 '17 at 9:58
Prashant Singh
10318
I have a dual boot of Windows and Ubuntu. When I switch on the machine, the BIOS does POST and after that the bootloader starts.
I want to understand how the BIOS chooses which bootloader to run. I want to know the process going on between the BIOS and the bootloader in a dual boot computer.
boot bootloader bios
boot bootloader bios
edited Nov 29 '17 at 19:43
karel
56.8k11126146
asked Nov 29 '17 at 9:58
Prashant Singh
10318
edited Nov 29 '17 at 19:43
karel
56.8k11126146
asked Nov 29 '17 at 9:58
Prashant Singh
10318
edited Nov 29 '17 at 19:43
karel
56.8k11126146
edited Nov 29 '17 at 19:43
karel
56.8k11126146
edited Nov 29 '17 at 19:43
karel
56.8k11126146
56.8k11126146
asked Nov 29 '17 at 9:58
Prashant Singh
10318
asked Nov 29 '17 at 9:58
Prashant Singh
10318
asked Nov 29 '17 at 9:58
Prashant Singh
10318
10318
6
I suggest you read en.wikipedia.org/wiki/Power-on_self-test , en.wikipedia.org/wiki/BIOS , en.wikipedia.org/wiki/Master_boot_record , en.wikipedia.org/wiki/GUID_Partition_Table , en.wikipedia.org/wiki/UEFI .
– waltinator
Nov 29 '17 at 14:00
add a comment |
6
I suggest you read en.wikipedia.org/wiki/Power-on_self-test , en.wikipedia.org/wiki/BIOS , en.wikipedia.org/wiki/Master_boot_record , en.wikipedia.org/wiki/GUID_Partition_Table , en.wikipedia.org/wiki/UEFI .
– waltinator
Nov 29 '17 at 14:00
6
6
I suggest you read en.wikipedia.org/wiki/Power-on_self-test , en.wikipedia.org/wiki/BIOS , en.wikipedia.org/wiki/Master_boot_record , en.wikipedia.org/wiki/GUID_Partition_Table , en.wikipedia.org/wiki/UEFI .
– waltinator
Nov 29 '17 at 14:00
I suggest you read en.wikipedia.org/wiki/Power-on_self-test , en.wikipedia.org/wiki/BIOS , en.wikipedia.org/wiki/Master_boot_record , en.wikipedia.org/wiki/GUID_Partition_Table , en.wikipedia.org/wiki/UEFI .
– waltinator
Nov 29 '17 at 14:00
add a comment |
3 Answers
3
active
oldest
votes
BIOS firmware doesn't really choose the bootloader. It loads code from sector 0 of a drive and executes it. Whatever is there, it will execute. Hopefully it is a bootloader (or something that loads a bootloader) but it doesn't have to be. In the early PC days you had games on floppy disks that would simply boot and run without an OS - these are now called "booters."
UEFI firmware actually understands partitions and filesystems, and scans drives for a UEFI System partition type. Since this is a filesystem, multiple bootloaders can be placed here. UEFI firmware is supposed to provide a menu or other way for you to select which bootloader is used.
Many UEFI systems are booting in "Legacy mode" - where the UEFI loads a "Compatibility Service Module" - something that makes it look like a BIOS - and actually work like the BIOS.
GRUB is a common open-source bootloader that can either boot Linux or "chainload" (give control to) a Windows bootloader (typically winload.exe in the Boot folder of a Windows partition). GRUB is what's giving you the ability to make a decision. GRUB can read configuration files and take its default choice from them.
Read this if you want copious, gory details.
answered Nov 29 '17 at 14:22
LawrenceC
46136
This is one of the reasons that, on Ubuntu, you needsudoor root to write anything to an unmounted disk; if a program or malicious user writes malware to the boot partition...
– wizzwizz4
Nov 30 '17 at 7:18
Thanks LawrenceC your explanation make my understanding more clear .thanks once again
– Prashant Singh
Dec 1 '17 at 6:51
add a comment |
This diagram shows how control passes from the firmware (BIOS or UEFI) to the bootloader and from the bootloader to the operating system in Ubuntu.
BIOS vs. UEFI
If the OSs were installed in different modes (BIOS and UEFI), dual booting Windows and Ubuntu can't work.
Review this answer and https://help.ubuntu.com/community/UEFI in the section about Converting Ubuntu into UEFI mode.
The grub bootloader can also be converted in the opposite direction from UEFI to BIOS. Linux can boot fine from a GPT disk in BIOS mode. See this answer: Convert from EFI to BIOS boot
answered Nov 29 '17 at 11:37
karel
56.8k11126146
add a comment |
In legacy mode (BIOS boot and not UEFI) BIOS controls the drive order. Once upon a time this used to be controlled by the cables; but changing a BIOS setting beats opening the box & changing cables.
BIOS loads (into memory) the first sector (512 bytes of disk called MBR or master boot record) of the first disk (or drive order controlled by BIOS) and then passes (CPU) control to this 'bootloader'. BIOS has thus completed its job and the code in the first sector runs.
edited Nov 29 '17 at 11:40
Zanna
50k13131238
answered Nov 29 '17 at 10:15
guiverc
4,06811522
SORRY sir but i am bit confuse as bios give control to the boot loader and window and linux have different boot loader so to which boot loader it give control .what process bios go through to choose the boot loader
– Prashant Singh
Nov 29 '17 at 10:47
2
Your system can only have a single boot loader per disk (and only one is ever active). Generally, if you have two operating systems on your system, the second one installed owns the boot-loader as it wrote its own code into the MBR. This is why GNU/Linux (Ubuntu) uses GRUB; its a multi-step system (step 1 is the MBR, steps 1.5 & 2 are found in /boot) that puts up menu asking which OS you want to load/run (the ones grub knows about anyway, plus whatever ISO's you've added to it). If you have two disk drives; you can have a boot loader on each drive, but BIOS will determine which will run.
– guiverc
Nov 29 '17 at 11:13
So if i have 2 operating system in my computer then is it necessary that GRUB will put up the menu asking which os i want to load why not window's boot loader put that menu as i have both os in my computer.
– Prashant Singh
Nov 29 '17 at 11:28
windows has a boot loader too (up to vista anyway); but its not as smart as grub is. the windoze version doesn't search for non-msft products (and can't read ext/reiserfs/xfs/zfs/btrfs/...) thus has you have to add the *nix yourself; and next update ..... the windoze version isn't worth using as grub is so much better. If windoze was on one drive, Ubuntu on the other you could alter the boot by BIOS; but grub is faster/easier. (if happy with my answer; accept it to close the question)
– guiverc
Nov 29 '17 at 11:33
3
@Prashant Singh: The most fundamental reason why the Windows bootloader doesn't do this (or didn't, back when I knew a bit about Windows) is that MicroSoft doesn't make money by letting you run other operating systems.
– jamesqf
Nov 30 '17 at 3:44
|
show 6 more comments
Your Answer
StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "89"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});
function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});
}
});
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2faskubuntu.com%2fquestions%2f981382%2fin-a-dual-boot-system-how-does-the-bios-choose-which-bootloader-to-run%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
BIOS firmware doesn't really choose the bootloader. It loads code from sector 0 of a drive and executes it. Whatever is there, it will execute. Hopefully it is a bootloader (or something that loads a bootloader) but it doesn't have to be. In the early PC days you had games on floppy disks that would simply boot and run without an OS - these are now called "booters."
UEFI firmware actually understands partitions and filesystems, and scans drives for a UEFI System partition type. Since this is a filesystem, multiple bootloaders can be placed here. UEFI firmware is supposed to provide a menu or other way for you to select which bootloader is used.
Many UEFI systems are booting in "Legacy mode" - where the UEFI loads a "Compatibility Service Module" - something that makes it look like a BIOS - and actually work like the BIOS.
GRUB is a common open-source bootloader that can either boot Linux or "chainload" (give control to) a Windows bootloader (typically winload.exe in the Boot folder of a Windows partition). GRUB is what's giving you the ability to make a decision. GRUB can read configuration files and take its default choice from them.
Read this if you want copious, gory details.
answered Nov 29 '17 at 14:22
LawrenceC
46136
This is one of the reasons that, on Ubuntu, you needsudoor root to write anything to an unmounted disk; if a program or malicious user writes malware to the boot partition...
– wizzwizz4
Nov 30 '17 at 7:18
Thanks LawrenceC your explanation make my understanding more clear .thanks once again
– Prashant Singh
Dec 1 '17 at 6:51
add a comment |
BIOS firmware doesn't really choose the bootloader. It loads code from sector 0 of a drive and executes it. Whatever is there, it will execute. Hopefully it is a bootloader (or something that loads a bootloader) but it doesn't have to be. In the early PC days you had games on floppy disks that would simply boot and run without an OS - these are now called "booters."
UEFI firmware actually understands partitions and filesystems, and scans drives for a UEFI System partition type. Since this is a filesystem, multiple bootloaders can be placed here. UEFI firmware is supposed to provide a menu or other way for you to select which bootloader is used.
Many UEFI systems are booting in "Legacy mode" - where the UEFI loads a "Compatibility Service Module" - something that makes it look like a BIOS - and actually work like the BIOS.
GRUB is a common open-source bootloader that can either boot Linux or "chainload" (give control to) a Windows bootloader (typically winload.exe in the Boot folder of a Windows partition). GRUB is what's giving you the ability to make a decision. GRUB can read configuration files and take its default choice from them.
Read this if you want copious, gory details.
answered Nov 29 '17 at 14:22
LawrenceC
46136
This is one of the reasons that, on Ubuntu, you needsudoor root to write anything to an unmounted disk; if a program or malicious user writes malware to the boot partition...
– wizzwizz4
Nov 30 '17 at 7:18
Thanks LawrenceC your explanation make my understanding more clear .thanks once again
– Prashant Singh
Dec 1 '17 at 6:51
add a comment |
BIOS firmware doesn't really choose the bootloader. It loads code from sector 0 of a drive and executes it. Whatever is there, it will execute. Hopefully it is a bootloader (or something that loads a bootloader) but it doesn't have to be. In the early PC days you had games on floppy disks that would simply boot and run without an OS - these are now called "booters."
UEFI firmware actually understands partitions and filesystems, and scans drives for a UEFI System partition type. Since this is a filesystem, multiple bootloaders can be placed here. UEFI firmware is supposed to provide a menu or other way for you to select which bootloader is used.
Many UEFI systems are booting in "Legacy mode" - where the UEFI loads a "Compatibility Service Module" - something that makes it look like a BIOS - and actually work like the BIOS.
GRUB is a common open-source bootloader that can either boot Linux or "chainload" (give control to) a Windows bootloader (typically winload.exe in the Boot folder of a Windows partition). GRUB is what's giving you the ability to make a decision. GRUB can read configuration files and take its default choice from them.
Read this if you want copious, gory details.
answered Nov 29 '17 at 14:22
LawrenceC
46136
BIOS firmware doesn't really choose the bootloader. It loads code from sector 0 of a drive and executes it. Whatever is there, it will execute. Hopefully it is a bootloader (or something that loads a bootloader) but it doesn't have to be. In the early PC days you had games on floppy disks that would simply boot and run without an OS - these are now called "booters."
UEFI firmware actually understands partitions and filesystems, and scans drives for a UEFI System partition type. Since this is a filesystem, multiple bootloaders can be placed here. UEFI firmware is supposed to provide a menu or other way for you to select which bootloader is used.
Many UEFI systems are booting in "Legacy mode" - where the UEFI loads a "Compatibility Service Module" - something that makes it look like a BIOS - and actually work like the BIOS.
GRUB is a common open-source bootloader that can either boot Linux or "chainload" (give control to) a Windows bootloader (typically winload.exe in the Boot folder of a Windows partition). GRUB is what's giving you the ability to make a decision. GRUB can read configuration files and take its default choice from them.
Read this if you want copious, gory details.
answered Nov 29 '17 at 14:22
LawrenceC
46136
answered Nov 29 '17 at 14:22
LawrenceC
46136
answered Nov 29 '17 at 14:22
LawrenceC
46136
answered Nov 29 '17 at 14:22
LawrenceC
46136
46136
This is one of the reasons that, on Ubuntu, you needsudoor root to write anything to an unmounted disk; if a program or malicious user writes malware to the boot partition...
– wizzwizz4
Nov 30 '17 at 7:18
Thanks LawrenceC your explanation make my understanding more clear .thanks once again
– Prashant Singh
Dec 1 '17 at 6:51
add a comment |
This is one of the reasons that, on Ubuntu, you needsudoor root to write anything to an unmounted disk; if a program or malicious user writes malware to the boot partition...
– wizzwizz4
Nov 30 '17 at 7:18
Thanks LawrenceC your explanation make my understanding more clear .thanks once again
– Prashant Singh
Dec 1 '17 at 6:51
This is one of the reasons that, on Ubuntu, you need
sudo or root to write anything to an unmounted disk; if a program or malicious user writes malware to the boot partition...– wizzwizz4
Nov 30 '17 at 7:18
This is one of the reasons that, on Ubuntu, you need
sudo or root to write anything to an unmounted disk; if a program or malicious user writes malware to the boot partition...– wizzwizz4
Nov 30 '17 at 7:18
Thanks LawrenceC your explanation make my understanding more clear .thanks once again
– Prashant Singh
Dec 1 '17 at 6:51
Thanks LawrenceC your explanation make my understanding more clear .thanks once again
– Prashant Singh
Dec 1 '17 at 6:51
add a comment |
This diagram shows how control passes from the firmware (BIOS or UEFI) to the bootloader and from the bootloader to the operating system in Ubuntu.
BIOS vs. UEFI
If the OSs were installed in different modes (BIOS and UEFI), dual booting Windows and Ubuntu can't work.
Review this answer and https://help.ubuntu.com/community/UEFI in the section about Converting Ubuntu into UEFI mode.
The grub bootloader can also be converted in the opposite direction from UEFI to BIOS. Linux can boot fine from a GPT disk in BIOS mode. See this answer: Convert from EFI to BIOS boot
answered Nov 29 '17 at 11:37
karel
56.8k11126146
add a comment |
This diagram shows how control passes from the firmware (BIOS or UEFI) to the bootloader and from the bootloader to the operating system in Ubuntu.
BIOS vs. UEFI
If the OSs were installed in different modes (BIOS and UEFI), dual booting Windows and Ubuntu can't work.
Review this answer and https://help.ubuntu.com/community/UEFI in the section about Converting Ubuntu into UEFI mode.
The grub bootloader can also be converted in the opposite direction from UEFI to BIOS. Linux can boot fine from a GPT disk in BIOS mode. See this answer: Convert from EFI to BIOS boot
answered Nov 29 '17 at 11:37
karel
56.8k11126146
add a comment |
This diagram shows how control passes from the firmware (BIOS or UEFI) to the bootloader and from the bootloader to the operating system in Ubuntu.
BIOS vs. UEFI
If the OSs were installed in different modes (BIOS and UEFI), dual booting Windows and Ubuntu can't work.
Review this answer and https://help.ubuntu.com/community/UEFI in the section about Converting Ubuntu into UEFI mode.
The grub bootloader can also be converted in the opposite direction from UEFI to BIOS. Linux can boot fine from a GPT disk in BIOS mode. See this answer: Convert from EFI to BIOS boot
answered Nov 29 '17 at 11:37
karel
56.8k11126146
This diagram shows how control passes from the firmware (BIOS or UEFI) to the bootloader and from the bootloader to the operating system in Ubuntu.
BIOS vs. UEFI
If the OSs were installed in different modes (BIOS and UEFI), dual booting Windows and Ubuntu can't work.
Review this answer and https://help.ubuntu.com/community/UEFI in the section about Converting Ubuntu into UEFI mode.
The grub bootloader can also be converted in the opposite direction from UEFI to BIOS. Linux can boot fine from a GPT disk in BIOS mode. See this answer: Convert from EFI to BIOS boot
answered Nov 29 '17 at 11:37
karel
56.8k11126146
edited Dec 9 at 19:05
answered Nov 29 '17 at 11:37
karel
56.8k11126146
answered Nov 29 '17 at 11:37
karel
56.8k11126146
answered Nov 29 '17 at 11:37
karel
56.8k11126146
56.8k11126146
add a comment |
add a comment |
In legacy mode (BIOS boot and not UEFI) BIOS controls the drive order. Once upon a time this used to be controlled by the cables; but changing a BIOS setting beats opening the box & changing cables.
BIOS loads (into memory) the first sector (512 bytes of disk called MBR or master boot record) of the first disk (or drive order controlled by BIOS) and then passes (CPU) control to this 'bootloader'. BIOS has thus completed its job and the code in the first sector runs.
edited Nov 29 '17 at 11:40
Zanna
50k13131238
answered Nov 29 '17 at 10:15
guiverc
4,06811522
SORRY sir but i am bit confuse as bios give control to the boot loader and window and linux have different boot loader so to which boot loader it give control .what process bios go through to choose the boot loader
– Prashant Singh
Nov 29 '17 at 10:47
2
Your system can only have a single boot loader per disk (and only one is ever active). Generally, if you have two operating systems on your system, the second one installed owns the boot-loader as it wrote its own code into the MBR. This is why GNU/Linux (Ubuntu) uses GRUB; its a multi-step system (step 1 is the MBR, steps 1.5 & 2 are found in /boot) that puts up menu asking which OS you want to load/run (the ones grub knows about anyway, plus whatever ISO's you've added to it). If you have two disk drives; you can have a boot loader on each drive, but BIOS will determine which will run.
– guiverc
Nov 29 '17 at 11:13
So if i have 2 operating system in my computer then is it necessary that GRUB will put up the menu asking which os i want to load why not window's boot loader put that menu as i have both os in my computer.
– Prashant Singh
Nov 29 '17 at 11:28
windows has a boot loader too (up to vista anyway); but its not as smart as grub is. the windoze version doesn't search for non-msft products (and can't read ext/reiserfs/xfs/zfs/btrfs/...) thus has you have to add the *nix yourself; and next update ..... the windoze version isn't worth using as grub is so much better. If windoze was on one drive, Ubuntu on the other you could alter the boot by BIOS; but grub is faster/easier. (if happy with my answer; accept it to close the question)
– guiverc
Nov 29 '17 at 11:33
3
@Prashant Singh: The most fundamental reason why the Windows bootloader doesn't do this (or didn't, back when I knew a bit about Windows) is that MicroSoft doesn't make money by letting you run other operating systems.
– jamesqf
Nov 30 '17 at 3:44
|
show 6 more comments
In legacy mode (BIOS boot and not UEFI) BIOS controls the drive order. Once upon a time this used to be controlled by the cables; but changing a BIOS setting beats opening the box & changing cables.
BIOS loads (into memory) the first sector (512 bytes of disk called MBR or master boot record) of the first disk (or drive order controlled by BIOS) and then passes (CPU) control to this 'bootloader'. BIOS has thus completed its job and the code in the first sector runs.
edited Nov 29 '17 at 11:40
Zanna
50k13131238
answered Nov 29 '17 at 10:15
guiverc
4,06811522
SORRY sir but i am bit confuse as bios give control to the boot loader and window and linux have different boot loader so to which boot loader it give control .what process bios go through to choose the boot loader
– Prashant Singh
Nov 29 '17 at 10:47
2
Your system can only have a single boot loader per disk (and only one is ever active). Generally, if you have two operating systems on your system, the second one installed owns the boot-loader as it wrote its own code into the MBR. This is why GNU/Linux (Ubuntu) uses GRUB; its a multi-step system (step 1 is the MBR, steps 1.5 & 2 are found in /boot) that puts up menu asking which OS you want to load/run (the ones grub knows about anyway, plus whatever ISO's you've added to it). If you have two disk drives; you can have a boot loader on each drive, but BIOS will determine which will run.
– guiverc
Nov 29 '17 at 11:13
So if i have 2 operating system in my computer then is it necessary that GRUB will put up the menu asking which os i want to load why not window's boot loader put that menu as i have both os in my computer.
– Prashant Singh
Nov 29 '17 at 11:28
windows has a boot loader too (up to vista anyway); but its not as smart as grub is. the windoze version doesn't search for non-msft products (and can't read ext/reiserfs/xfs/zfs/btrfs/...) thus has you have to add the *nix yourself; and next update ..... the windoze version isn't worth using as grub is so much better. If windoze was on one drive, Ubuntu on the other you could alter the boot by BIOS; but grub is faster/easier. (if happy with my answer; accept it to close the question)
– guiverc
Nov 29 '17 at 11:33
3
@Prashant Singh: The most fundamental reason why the Windows bootloader doesn't do this (or didn't, back when I knew a bit about Windows) is that MicroSoft doesn't make money by letting you run other operating systems.
– jamesqf
Nov 30 '17 at 3:44
|
show 6 more comments
In legacy mode (BIOS boot and not UEFI) BIOS controls the drive order. Once upon a time this used to be controlled by the cables; but changing a BIOS setting beats opening the box & changing cables.
BIOS loads (into memory) the first sector (512 bytes of disk called MBR or master boot record) of the first disk (or drive order controlled by BIOS) and then passes (CPU) control to this 'bootloader'. BIOS has thus completed its job and the code in the first sector runs.
edited Nov 29 '17 at 11:40
Zanna
50k13131238
answered Nov 29 '17 at 10:15
guiverc
4,06811522
In legacy mode (BIOS boot and not UEFI) BIOS controls the drive order. Once upon a time this used to be controlled by the cables; but changing a BIOS setting beats opening the box & changing cables.
BIOS loads (into memory) the first sector (512 bytes of disk called MBR or master boot record) of the first disk (or drive order controlled by BIOS) and then passes (CPU) control to this 'bootloader'. BIOS has thus completed its job and the code in the first sector runs.
edited Nov 29 '17 at 11:40
Zanna
50k13131238
answered Nov 29 '17 at 10:15
guiverc
4,06811522
edited Nov 29 '17 at 11:40
Zanna
50k13131238
edited Nov 29 '17 at 11:40
Zanna
50k13131238
edited Nov 29 '17 at 11:40
Zanna
50k13131238
50k13131238
answered Nov 29 '17 at 10:15
guiverc
4,06811522
answered Nov 29 '17 at 10:15
guiverc
4,06811522
answered Nov 29 '17 at 10:15
guiverc
4,06811522
4,06811522
SORRY sir but i am bit confuse as bios give control to the boot loader and window and linux have different boot loader so to which boot loader it give control .what process bios go through to choose the boot loader
– Prashant Singh
Nov 29 '17 at 10:47
2
Your system can only have a single boot loader per disk (and only one is ever active). Generally, if you have two operating systems on your system, the second one installed owns the boot-loader as it wrote its own code into the MBR. This is why GNU/Linux (Ubuntu) uses GRUB; its a multi-step system (step 1 is the MBR, steps 1.5 & 2 are found in /boot) that puts up menu asking which OS you want to load/run (the ones grub knows about anyway, plus whatever ISO's you've added to it). If you have two disk drives; you can have a boot loader on each drive, but BIOS will determine which will run.
– guiverc
Nov 29 '17 at 11:13
So if i have 2 operating system in my computer then is it necessary that GRUB will put up the menu asking which os i want to load why not window's boot loader put that menu as i have both os in my computer.
– Prashant Singh
Nov 29 '17 at 11:28
windows has a boot loader too (up to vista anyway); but its not as smart as grub is. the windoze version doesn't search for non-msft products (and can't read ext/reiserfs/xfs/zfs/btrfs/...) thus has you have to add the *nix yourself; and next update ..... the windoze version isn't worth using as grub is so much better. If windoze was on one drive, Ubuntu on the other you could alter the boot by BIOS; but grub is faster/easier. (if happy with my answer; accept it to close the question)
– guiverc
Nov 29 '17 at 11:33
3
@Prashant Singh: The most fundamental reason why the Windows bootloader doesn't do this (or didn't, back when I knew a bit about Windows) is that MicroSoft doesn't make money by letting you run other operating systems.
– jamesqf
Nov 30 '17 at 3:44
|
show 6 more comments
SORRY sir but i am bit confuse as bios give control to the boot loader and window and linux have different boot loader so to which boot loader it give control .what process bios go through to choose the boot loader
– Prashant Singh
Nov 29 '17 at 10:47
2
Your system can only have a single boot loader per disk (and only one is ever active). Generally, if you have two operating systems on your system, the second one installed owns the boot-loader as it wrote its own code into the MBR. This is why GNU/Linux (Ubuntu) uses GRUB; its a multi-step system (step 1 is the MBR, steps 1.5 & 2 are found in /boot) that puts up menu asking which OS you want to load/run (the ones grub knows about anyway, plus whatever ISO's you've added to it). If you have two disk drives; you can have a boot loader on each drive, but BIOS will determine which will run.
– guiverc
Nov 29 '17 at 11:13
So if i have 2 operating system in my computer then is it necessary that GRUB will put up the menu asking which os i want to load why not window's boot loader put that menu as i have both os in my computer.
– Prashant Singh
Nov 29 '17 at 11:28
windows has a boot loader too (up to vista anyway); but its not as smart as grub is. the windoze version doesn't search for non-msft products (and can't read ext/reiserfs/xfs/zfs/btrfs/...) thus has you have to add the *nix yourself; and next update ..... the windoze version isn't worth using as grub is so much better. If windoze was on one drive, Ubuntu on the other you could alter the boot by BIOS; but grub is faster/easier. (if happy with my answer; accept it to close the question)
– guiverc
Nov 29 '17 at 11:33
3
@Prashant Singh: The most fundamental reason why the Windows bootloader doesn't do this (or didn't, back when I knew a bit about Windows) is that MicroSoft doesn't make money by letting you run other operating systems.
– jamesqf
Nov 30 '17 at 3:44
SORRY sir but i am bit confuse as bios give control to the boot loader and window and linux have different boot loader so to which boot loader it give control .what process bios go through to choose the boot loader
– Prashant Singh
Nov 29 '17 at 10:47
SORRY sir but i am bit confuse as bios give control to the boot loader and window and linux have different boot loader so to which boot loader it give control .what process bios go through to choose the boot loader
– Prashant Singh
Nov 29 '17 at 10:47
2
2
Your system can only have a single boot loader per disk (and only one is ever active). Generally, if you have two operating systems on your system, the second one installed owns the boot-loader as it wrote its own code into the MBR. This is why GNU/Linux (Ubuntu) uses GRUB; its a multi-step system (step 1 is the MBR, steps 1.5 & 2 are found in /boot) that puts up menu asking which OS you want to load/run (the ones grub knows about anyway, plus whatever ISO's you've added to it). If you have two disk drives; you can have a boot loader on each drive, but BIOS will determine which will run.
– guiverc
Nov 29 '17 at 11:13
Your system can only have a single boot loader per disk (and only one is ever active). Generally, if you have two operating systems on your system, the second one installed owns the boot-loader as it wrote its own code into the MBR. This is why GNU/Linux (Ubuntu) uses GRUB; its a multi-step system (step 1 is the MBR, steps 1.5 & 2 are found in /boot) that puts up menu asking which OS you want to load/run (the ones grub knows about anyway, plus whatever ISO's you've added to it). If you have two disk drives; you can have a boot loader on each drive, but BIOS will determine which will run.
– guiverc
Nov 29 '17 at 11:13
So if i have 2 operating system in my computer then is it necessary that GRUB will put up the menu asking which os i want to load why not window's boot loader put that menu as i have both os in my computer.
– Prashant Singh
Nov 29 '17 at 11:28
So if i have 2 operating system in my computer then is it necessary that GRUB will put up the menu asking which os i want to load why not window's boot loader put that menu as i have both os in my computer.
– Prashant Singh
Nov 29 '17 at 11:28
windows has a boot loader too (up to vista anyway); but its not as smart as grub is. the windoze version doesn't search for non-msft products (and can't read ext/reiserfs/xfs/zfs/btrfs/...) thus has you have to add the *nix yourself; and next update ..... the windoze version isn't worth using as grub is so much better. If windoze was on one drive, Ubuntu on the other you could alter the boot by BIOS; but grub is faster/easier. (if happy with my answer; accept it to close the question)
– guiverc
Nov 29 '17 at 11:33
windows has a boot loader too (up to vista anyway); but its not as smart as grub is. the windoze version doesn't search for non-msft products (and can't read ext/reiserfs/xfs/zfs/btrfs/...) thus has you have to add the *nix yourself; and next update ..... the windoze version isn't worth using as grub is so much better. If windoze was on one drive, Ubuntu on the other you could alter the boot by BIOS; but grub is faster/easier. (if happy with my answer; accept it to close the question)
– guiverc
Nov 29 '17 at 11:33
3
3
@Prashant Singh: The most fundamental reason why the Windows bootloader doesn't do this (or didn't, back when I knew a bit about Windows) is that MicroSoft doesn't make money by letting you run other operating systems.
– jamesqf
Nov 30 '17 at 3:44
@Prashant Singh: The most fundamental reason why the Windows bootloader doesn't do this (or didn't, back when I knew a bit about Windows) is that MicroSoft doesn't make money by letting you run other operating systems.
– jamesqf
Nov 30 '17 at 3:44
|
show 6 more comments
Thanks for contributing an answer to Ask Ubuntu!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
To learn more, see our tips on writing great answers.
Some of your past answers have not been well-received, and you're in danger of being blocked from answering.
Please pay close attention to the following guidance:
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2faskubuntu.com%2fquestions%2f981382%2fin-a-dual-boot-system-how-does-the-bios-choose-which-bootloader-to-run%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
6
I suggest you read en.wikipedia.org/wiki/Power-on_self-test , en.wikipedia.org/wiki/BIOS , en.wikipedia.org/wiki/Master_boot_record , en.wikipedia.org/wiki/GUID_Partition_Table , en.wikipedia.org/wiki/UEFI .
– waltinator
Nov 29 '17 at 14:00