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Dual booting problem

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  Dual booting problem Van Snyder <van.snyder@sbcglobal.net> - 2025-06-30 23:10 +0200
    Re: Dual booting problem Felix Miata <mrmazda@stanis.net> - 2025-06-30 23:30 +0200
      Re: Dual booting problem Felix Miata <mrmazda@earthlink.net> - 2025-07-01 01:10 +0200
    Re: Dual booting problem David Christensen <dpchrist@holgerdanske.com> - 2025-07-01 02:40 +0200
      Re: Dual booting problem David Christensen <dpchrist@holgerdanske.com> - 2025-07-01 02:50 +0200

#280512 — Dual booting problem

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I'm working on an ASUS computer for a deceased colleague's widow.

He had Fedora 28 on a HDD. I installed Debian 12 on an NVME drive. She
also wanted Windoze 11 so I installed it on another NVME drive.

The boot mode was set to "legacy" but the Windoze installer DVD
wouldn't even boot until it was changed to "UEFI" and then the Debian
DVD wouldn't boot in UEFI so I changed the boot mode to UEFI/Legacy.
The Windoze drive has a FAT32 EFI partition.

update-grub doesn't see the Windoze install. I manually added menuitems
in /etc/grub.d/40_custom using the partition's UUID (search --fs-uuid)
and the partition's label (search --fs-label). None of them work.
During boot, grub says the boot file doesn't exist, but when I boot
Debian and look in the Windoze EFI partition, it's there.

The Fedora and Debian installs are non-EFI, so there's no EFI grub.

I tried to add the Debian partition to the Windoze boot manager using
bcdedit and easyBCD but neither one could see it.

If I want to have dual boot, instead of telling the BIOS which
partition to boot, must I essentially start over with the Debian
install i EFI mode (if I can find an installer DVD that will boot EFI)?
I don't want to muck with the Fedora install. If I get a Debian EFI
install done, will its grub-update be able to see the Fedora
installation?

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#280513

Van Snyder composed on 2025-06-30 13:59 (UTC-0700):

> If I want to have dual boot, instead of telling the BIOS which
> partition to boot, must I essentially start over with the Debian
> install i EFI mode (if I can find an installer DVD that will boot EFI)?
> I don't want to muck with the Fedora install. If I get a Debian EFI
> install done, will its grub-update be able to see the Fedora
> installation?

Debian needs to be installed in UEFI mode for its Grub to be able to chain Win11's
bootloader. Debian should have no problem loading Fedora's kernel and initrd via
40_custom if necessary due to Fedora having been installed in legacy mode, if that
was the case, or in UEFI mode but not using Grub, if that was the case. If Fedora
was installed in UEFI mode with Grub, then Debian's os-prober should pick it up
automatically, once os-prober is enabled, which would need to be changed from the
"safe" disabled default (/etc/default/grub's GRUB_DISABLE_OS_PROBER="true").
-- 
Evolution as taught in public schools is, like religion,
	based on faith, not based on science.

 Team OS/2 ** Reg. Linux User #211409 ** a11y rocks!

Felix Miata

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#280514

Van Snyder composed on 2025-06-30 14:46 (UTC-0700):

> On Mon, 2025-06-30 at 17:26 -0400, Felix Miata wrote:

>> Debian needs to be installed in UEFI mode for its Grub to be able to>> chain Win11's
>> bootloader. 

> The netinst Debian 12 DVD I downloaded wouldn't boot in EFI mode. How
> do I install Debian 12 in EFI mode. Can I change it after it's
> installed?

AFAIK, Debian doesn't make any installation .isos for Stable amd64 that will not
boot in UEFI mode. What probably happened to you is one of two or more things:

1-incomplete burning of .iso to USB media. Just because the burner program claims
it's done doesn't necessarily mean the writing to the USB is complete. You must
ensure the OS reports safe first. I ensure this by issuing the sync command after
the write utility's claim of completion occurs. Only when sync returns is it sure
to be truly safe to "safely" remove the device, or to reboot. As USB sticks are
notoriously unreliable, I do my .iso writing to them using ddrescue instead of
plain dd or any of the GUI tools designed for the task.

2-you didn't try hard enough. One way to ensure you don't boot in CSM/legacy mode
is to disable it in the UEFI BIOS. Another way to be sure is to use the BBS hotkey
to select the boot device. UEFI capable media will normally show up in that menu
(at least) twice, once with, and once without, a UEFI moniker. Simply select that
which has a UEFI moniker included.

3-USB3 sticks can't be expected to work properly in USB2 ports.

If Fedora was installed in UEFI mode, you can use its bootloader to start a Debian
installation by loading the linux and initrd.gz taken either from the NET
installation media, or its mirrors counterpart:
<http://ftp.us.debian.org/debian/dists/bookworm/main/installer-amd64/current/images/netboot/debian-installer/amd64/>

Loading linux and initrd.gz with Grub is how most of my Linux installations begin.
The following is (approximately) an EFI Grub2 stanza I previously used for the
purpose:
menuentry "Install Debian via HTTP" {
	search --no-floppy --label --set=root tm8p03res
	linuxefi	/deb/linux showopts vga=791 --- net.ifnames=0 ipv6.disable=1
netcfg/get_hostname=myhost netcfg/get_domain=mydomain.net
netcfg/disable_autoconfig=true netcfg/get_ipaddress=192.168.###.###/24
netcfg/get_gateway=192.168.###.### netcfg/get_nameservers=1.0.0.1
netcfg/confirm_static=true tasks=standard base-installer/install-recommends=false
GRUB_DISABLE_OS_PROBER=true
	initrdefi	/deb/initrd.gz
}
Most of those linu line options are not necessary, but simply those I prefer be
utilized to get a simple base installation working before adding selected
non-essentials.
-- 
Evolution as taught in public schools is, like religion,
	based on faith, not based on science.

 Team OS/2 ** Reg. Linux User #211409 ** a11y rocks!

Felix Miata

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#280515

On 6/30/25 13:59, Van Snyder wrote:
> I'm working on an ASUS computer for a deceased colleague's widow.
> 
> He had Fedora 28 on a HDD. I installed Debian 12 on an NVME drive. She
> also wanted Windoze 11 so I installed it on another NVME drive.
> 
> The boot mode was set to "legacy" but the Windoze installer DVD
> wouldn't even boot until it was changed to "UEFI" and then the Debian
> DVD wouldn't boot in UEFI so I changed the boot mode to UEFI/Legacy.
> The Windoze drive has a FAT32 EFI partition.
> 
> update-grub doesn't see the Windoze install. I manually added menuitems
> in /etc/grub.d/40_custom using the partition's UUID (search --fs-uuid)
> and the partition's label (search --fs-label). None of them work.
> During boot, grub says the boot file doesn't exist, but when I boot
> Debian and look in the Windoze EFI partition, it's there.
> 
> The Fedora and Debian installs are non-EFI, so there's no EFI grub.
> 
> I tried to add the Debian partition to the Windoze boot manager using
> bcdedit and easyBCD but neither one could see it.
> 
> If I want to have dual boot, instead of telling the BIOS which
> partition to boot, must I essentially start over with the Debian
> install i EFI mode (if I can find an installer DVD that will boot EFI)?
> I don't want to muck with the Fedora install. If I get a Debian EFI
> install done, will its grub-update be able to see the Fedora
> installation?


+1 for multi-boot via multiple drives.


Mobile racks facilitate changing drives:

https://www.startech.com/en-us/hdd/mobile-racks

https://www.startech.com/en-us/hdd/m2-removable-pcie-n1


Keeping data on a file server or NAS allows you to access the data from 
whatever device or OS you are using.  If the owner does not have/want 
such, put the data on dedicated drive(s) and use common-denominator 
techniques -- motherboard HBA/RAID, NTFS.


David

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#280516

On 6/30/25 17:36, David Christensen wrote:
> +1 for multi-boot via multiple drives.
> 
> 
> Mobile racks facilitate changing drives:
> 
> https://www.startech.com/en-us/hdd/mobile-racks
> 
> https://www.startech.com/en-us/hdd/m2-removable-pcie-n1


I should add -- only insert one bootable drive at a time.  This 
eliminates the problem of OS updaters/ bootloaders stomping on each other.


David

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