this post was submitted on 25 Mar 2024
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    That's why we need two ssds for dual boot (lemmy.world)
    submitted 7 months ago by Waffelson@lemmy.world to c/linuxmemes@lemmy.world
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    [–] BCsven@lemmy.ca 28 points 7 months ago* (last edited 7 months ago) (1 children)
    • install windows
    • adjust main partition so you have space for Linux
    • install linux, during install create anither efi partition, and root partition.
    • linux probes foreign OS (some distros might not) and creates a chainloader entry from your new EFI to Windows EFI
    • set BIOS to boot from linux EFI

    Windows never knows the other partition exists and leaves it intact.

    [–] meliodas_101@lemmy.world 4 points 7 months ago (2 children)

    Could you give me more detail for step 3?

    [–] jose1324@lemmy.world 9 points 7 months ago (3 children)

    Don't even have to do that. Install windows first, then install Linux with refind bootloader on preferably a separate disk. Done

    [–] meliodas_100@lemmynsfw.com 2 points 7 months ago

    Did exactly that.

    [–] BCsven@lemmy.ca 0 points 7 months ago* (last edited 7 months ago) (1 children)

    You do need a separate EFI, even though linux finds EFI, otherwise windows update trashes it randomly and why the meme we see here exists, with separate EFI windows doesn't know about it. You can shutdown windows mid update and boot linux, then reboot back to windows and update will continue. Siloed System

    [–] jose1324@lemmy.world 2 points 7 months ago (1 children)

    That's literally what I did yesterday with my method. It works, Windows has never trashed it

    [–] BCsven@lemmy.ca 2 points 7 months ago* (last edited 7 months ago) (1 children)

    It will, thats why that meme exists.

    Not during typically reboots, but when some windows update or autofile repair happens it thinks it is the only OS on that partition and does what it likes.

    [–] jose1324@lemmy.world 1 points 7 months ago (1 children)

    Nope, ran it like this for over 5 years. Definitely rebooted during updates / did some crap

    [–] BCsven@lemmy.ca 0 points 7 months ago (1 children)

    Then you have been lucky, because most peoples experience with grub EFI on Windows partition is windows will eventually scrub it.

    [–] jose1324@lemmy.world 1 points 7 months ago (1 children)

    I'm not using Grub

    [–] BCsven@lemmy.ca 0 points 7 months ago

    Makes no difference of what bootloader, just that windows thimks it owns that partition

    [–] meliodas_101@lemmy.world 0 points 7 months ago (1 children)

    I installed arch so that didn't happen.

    [–] jose1324@lemmy.world 1 points 7 months ago

    Not how it works

    [–] BCsven@lemmy.ca 2 points 7 months ago (1 children)

    Yes. When you install Linux it will auto detect the Windows EFI partition and put boot stuff there by default, but then windows comes along and will randomly trash that setup. So during install don't go with the suggested option, instead use the partitioning tool to creat another small EFI boot partition elswhere on disk, leaving Windows EFI and OS paetitions as is. Also create your root and home partition(s). Install to those partitions, then Linux should prompt for Probe Foreign OS and add a chainloader entry to your grub menu. This entry, when selected, points grub to windows EFI partition ID and hands off the boot process to Windows. Windows is unaware it has been chainloaded. As long as you set BIOS to load directly from the LINUX EFI entry then you will boot to Grub with Linux/Windows Dual option...But technically it is not a true Dual Boot, it is a sequential boot I guess. I have had this for 7 years on same install and boot between W10 and Linux daily. Windows has never touched my Linux EFI.

    [–] meliodas_100@lemmynsfw.com 1 points 7 months ago (2 children)

    How to add chainloader entry to grub?

    [–] BCsven@lemmy.ca 1 points 7 months ago

    I responded how to via another comment, but wanted to mention that you may have a chainload to Windows already with your dual boot, but the main point was using two EFI partitions and chainloading to the other one, so Windows isn't ever in charge of files in your linux boot partition

    [–] BCsven@lemmy.ca 1 points 7 months ago* (last edited 7 months ago)

    For something like OpenSUSE you go into YAST2-GUI and click the probe foreign OS and then it asks you if you want Windows or Linux as the default boot. But to do it manually you add a menu entry to /boot/grub2/custom.cfg. or in /etc/grub.d/40_custom. After editing this you will have to run grub2-mkconfig -o /boot/grub2/grub.cfg which will compile all the grub info into /etc/grub2/grub.cfg I believe the custom.cfg entries end up after the 40_custom entries that the OS may have included. There is a persistent method entry if you did want to edit the /etc/grub2/grub.cfg directly, but probably not advised.

    Here is my entry for Windows boot partition and location of MS boot. Also below that is a UEFI entry for geting back to the BIOS, not relevent to this topic, but just so you see how the menu entries are defined. In my system these are at the end of all the other Linux entries.

    ### BEGIN /etc/grub.d/30_os-prober ###
menuentry 'Windows Boot Manager (on /dev/nvme0n1p2)' --class windows --class os $menuentry_id_option 'osprober-efi-4E48-193F' {
	insmod part_gpt
	insmod fat
	search --no-floppy --fs-uuid --set=root 4E48-193F
	chainloader /efi/Microsoft/Boot/bootmgfw.efi
}
### END /etc/grub.d/30_os-prober ###

### BEGIN /etc/grub.d/30_uefi-firmware ###
menuentry 'UEFI Firmware Settings' $menuentry_id_option 'uefi-firmware' {
	fwsetup
}