No. You can have more than one EFI system partition with separate bootloaders on each drive and set their boot order in the BIOS, just like booting from USB or anything else.
This is also possible with just one drive. The efi boot entries for each OS are stored separately in the efi system partition.
You can pull the linux drive, boot from the windows drive, and if one of the firmware updates was for efi, windows will trash the entry for your Linux disk.
This has happened for me many times, I had to use a grub rescue disk to rebuild the efi table.
The boot entries live in firmware yes, efibootmgr can create and remove them. The are pointers to the bootloader. Many systems can boot from the disk itself without the entry, the entry just makes it pretty (“Fedora” instead of NVME1).
Somewhat. One, a system can be bootable without the entries because they are just pointers to the actual bootloader, so even if windows does the stupid and deletes them it isn’t the end of the world. It does depend on your specific firmware though.
Also two, you can write them again with a single line in efibootmgr, they’re just saying “if I click Fedora load the shim from the EFI system partition on disk 1”.
This is very different than the old world where windows would delete your bootloader entirely and the MBR couldn’t be easily explored. They live in the efi system partition instead - or at least the shim does- and typically every OS leaves the other ones alone (even Windows, except in this case, although it didn’t touch the shim itself).
The initial comment was about the bootloader and really only applies to MBR partitions.
even if you have two drives, you still have only one bootloader, not?
The idea is to have completely separate boot and OS drives. You select which one you want to boot through the BIOS boot selection (ie. pressing F10 or F11 at the BIOS screen).
This functionally makes each OS “unaware” of the other one.
Unfortunately it really doesn’t. And it’s actually Linux that’s the bigger problem: whenever it decides to updates GRUB it looks for OSes on all of your drives to make grub entries for them. It also doesn’t necessarily modify the version of grub on the booted drive.
Yes I’m sure there’s a way to manually configure everything perfectly but my goal is a setup where I don’t have to constantly manually fix things.
My install does not seem to do this. I removed the windows drive when installing Linux on a new drive. Put both drives in and select which one to boot in the bios. Its been that way for about a year and, so far, grub updates have never noticed the windows install nor added to grub.
That’s with bazzite, can’t speak for any other distro as that is the only dual-boot machine I own. Bazzite does mention they do not recommend traditional dual boot with the boot loader and recommend the bios method so maybe they have something changed to avoid that?
If you install each OS with it’s own drive as the boot device, then you won’t see this issue.
Unless you boot Windows via the grub boot menu. If you do that then Windows will see that drive as the boot device.
If you select the OS by using the BIOS boot selection then you won’t see this issue.
I was bitten by Windows doing exactly this almost 15 years ago. Since that day if I ever had a need for dual-boot (even if running different distros) each OS will get it’s own dedicated drive, and I select what I want to boot through the BBS (BIOS Boot Selection). It’s usually invoked with F10 or F11 (but could be a different key combo.
While I generally agree with that, that’s not what seems to be happening here. What seems to be happening is that anyone who boots Windows via grub is getting grub itself overwritten.
When you install Linux, boot loaders like grub generally are smart and try to be helpful by scanning all available OSes and provide a boot menu entry for those. This is generally to help new users who install a dual-boot system and help them not think that “Linux erased Windows” when they see the new grub boot loader.
When you boot Windows from grub, Windows treats the drive with grub (where it booted from) as the boot drive. But if you tell your BIOS to boot the Windows drive, then grub won’t be invoked and Windows will boot seeing it’s own drive as the boot drive.
This is mostly an assumption as this hasn’t happened to me and details are still a bit scarce.
You can have a own EFI partition per Drive (and on it whatever bootloader you want). You then need to use the UEFI boot menu if you want e.g. boot the Windows one.
If you have 2 different OS on different drives they should never interfere with each other.
Well, i mean you could of course use the Linux Bootmanager to then forward to the Windows boot manager on the other disk. but i never experimented with that.
I just learned that you can do this setup even on one drive alone (having two bootloader on one drive in two partition and choosing in UEFI/Legacy BIOS)
But having 2 drives does not solve the boot loading issue, I mean, even if you have two drives, you still have only one bootloader, not?
No. You can have more than one EFI system partition with separate bootloaders on each drive and set their boot order in the BIOS, just like booting from USB or anything else.
This is also possible with just one drive. The efi boot entries for each OS are stored separately in the efi system partition.
EFI can also live in firmware memory.
You can pull the linux drive, boot from the windows drive, and if one of the firmware updates was for efi, windows will trash the entry for your Linux disk.
This has happened for me many times, I had to use a grub rescue disk to rebuild the efi table.
The boot entries live in firmware yes, efibootmgr can create and remove them. The are pointers to the bootloader. Many systems can boot from the disk itself without the entry, the entry just makes it pretty (“Fedora” instead of NVME1).
I’m not exactly sure what you’re suggesting. Isn’t that more or less what I just said?
Somewhat. One, a system can be bootable without the entries because they are just pointers to the actual bootloader, so even if windows does the stupid and deletes them it isn’t the end of the world. It does depend on your specific firmware though.
Also two, you can write them again with a single line in efibootmgr, they’re just saying “if I click Fedora load the shim from the EFI system partition on disk 1”.
This is very different than the old world where windows would delete your bootloader entirely and the MBR couldn’t be easily explored. They live in the efi system partition instead - or at least the shim does- and typically every OS leaves the other ones alone (even Windows, except in this case, although it didn’t touch the shim itself).
The initial comment was about the bootloader and really only applies to MBR partitions.
The idea is to have completely separate boot and OS drives. You select which one you want to boot through the BIOS boot selection (ie. pressing F10 or F11 at the BIOS screen).
This functionally makes each OS “unaware” of the other one.
Unfortunately it really doesn’t. And it’s actually Linux that’s the bigger problem: whenever it decides to updates GRUB it looks for OSes on all of your drives to make grub entries for them. It also doesn’t necessarily modify the version of grub on the booted drive.
Yes I’m sure there’s a way to manually configure everything perfectly but my goal is a setup where I don’t have to constantly manually fix things.
My install does not seem to do this. I removed the windows drive when installing Linux on a new drive. Put both drives in and select which one to boot in the bios. Its been that way for about a year and, so far, grub updates have never noticed the windows install nor added to grub.
That’s with bazzite, can’t speak for any other distro as that is the only dual-boot machine I own. Bazzite does mention they do not recommend traditional dual boot with the boot loader and recommend the bios method so maybe they have something changed to avoid that?
If you install each OS with it’s own drive as the boot device, then you won’t see this issue.
Unless you boot Windows via the grub boot menu. If you do that then Windows will see that drive as the boot device.
If you select the OS by using the BIOS boot selection then you won’t see this issue.
I was bitten by Windows doing exactly this almost 15 years ago. Since that day if I ever had a need for dual-boot (even if running different distros) each OS will get it’s own dedicated drive, and I select what I want to boot through the BBS (BIOS Boot Selection). It’s usually invoked with F10 or F11 (but could be a different key combo.
Oh you sweet sweet summer boy…
We’re talking Microsoft here, they’ll make sure they’re aware and they’ll make sure to f you over because Microsoft
While I generally agree with that, that’s not what seems to be happening here. What seems to be happening is that anyone who boots Windows via grub is getting grub itself overwritten.
When you install Linux, boot loaders like grub generally are smart and try to be helpful by scanning all available OSes and provide a boot menu entry for those. This is generally to help new users who install a dual-boot system and help them not think that “Linux erased Windows” when they see the new grub boot loader.
When you boot Windows from grub, Windows treats the drive with grub (where it booted from) as the boot drive. But if you tell your BIOS to boot the Windows drive, then grub won’t be invoked and Windows will boot seeing it’s own drive as the boot drive.
This is mostly an assumption as this hasn’t happened to me and details are still a bit scarce.
I did that and a Windows update nuked Linux from the BIOS boot loader a few weeks ago.
The only safe option is to have completely separate machines. Thankfully with the rise of ridiculously powerful minipcs that’s easier than ever.
You can have a own EFI partition per Drive (and on it whatever bootloader you want). You then need to use the UEFI boot menu if you want e.g. boot the Windows one. If you have 2 different OS on different drives they should never interfere with each other.
Well, i mean you could of course use the Linux Bootmanager to then forward to the Windows boot manager on the other disk. but i never experimented with that.
I just learned that you can do this setup even on one drive alone (having two bootloader on one drive in two partition and choosing in UEFI/Legacy BIOS)