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Thread: Dualboot WITHOUT Grub??

  1. #1
    Join Date
    Oct 2012
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    Dualboot WITHOUT Grub??

    Hi there

    I want to install Ubuntu 21.10 *without* the installer installing Grub. I currently have Windows 11 on a 2TB SSD and want to install Ubuntu for testing on a 240GB SSD.

    I want to be able to select my OS via the BIOS (UEFI) boot selection tool.

    I don't want any dramas if I decide to get rid of Ubuntu, which is why no GRUB!

    Cheers
    Last edited by zamfp; October 17th, 2021 at 07:34 AM.

  2. #2
    Join Date
    May 2008
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    2,126
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    Ubuntu 20.04 Focal Fossa

    Re: Dualboot WITHOUT Grub??

    Your intention to keep Ubuntu and Windows 11 separate is a sound choice.
    Here is a little check list:-

    De-activate, disconnect, isolate or physically remove existing Windows OS drive so that only the target drive is accessible
    Boot Ubuntu live and check that you are in UEFI mode
    Open a terminal and enter:-
    Code:
    [ -d /sys/firmware/efi ] && echo "UEFI" || echo "Legacy"
    Create GPT on your target disk using gparted
    Open gparted > Device > Create Partition Table > Select gpt
    Allow the installer to automatically create the necessary partitions (or your preferred configuration)
    Double check that an EFI partition will be created
    Boot each system independently via UEFI boot screen (ideal not cumbersome)
    Boot priority can be controlled by UEFI
    Each OS should be installed in UEFI mode with GPT
    Each drive should have EFI partition
    Each drive should have boot manager (Windows Boot Manager and Grub for Ubuntu)
    De-activate, disconnect, isolate or physically remove one drive so that you can check if the other boots independently (and vice versa)

    Grub will be installed otherwise you would not be able to boot Ubuntu.
    You will have to be vigilant with updates (especially grub updates).
    If your Windows drive is visible during a kernel or grub update, then it will probably take control of the boot process for both systems.

  3. #3
    Join Date
    Oct 2012
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    15

    Re: Dualboot WITHOUT Grub??

    Thanks for the reply.

    I cannot disconnect the drive as it's NVME and I'm not comfortable removing it. Any other options??

    Thanks

  4. #4
    Join Date
    May 2008
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    2,126
    Distro
    Ubuntu 20.04 Focal Fossa

    Re: Dualboot WITHOUT Grub??

    You may be able to de-activate the nvme Windows drive in your UEFI settings.

    Device > PCI (or similar as attachment)
    Attached Images Attached Images

  5. #5
    Join Date
    Oct 2012
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    15

    Re: Dualboot WITHOUT Grub??

    Thanks for your help! I looked and there is no setting there, unfortunately

  6. #6
    Join Date
    Aug 2011
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    6,087
    Distro
    Xubuntu 20.04 Focal Fossa

    Re: Dualboot WITHOUT Grub??

    Can the Windows drive be disabled in UEFI? That should work. Otherwise, grub will be installed on the EFI partition of the Windows drive, even if you select the Ubuntu drive for that. It's considered a bug. It's not too bad though. Back in the BIOS days, installing one bootloader would overwrite the other, but with UEFI multiple bootloaders can be together in one EFI partition. When you remove Ubuntu, just switch back to the Windows bootloader.

  7. #7
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    Oct 2012
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    Re: Dualboot WITHOUT Grub??

    Quote Originally Posted by Impavidus View Post
    Can the Windows drive be disabled in UEFI? That should work. Otherwise, grub will be installed on the EFI partition of the Windows drive, even if you select the Ubuntu drive for that. It's considered a bug. It's not too bad though. Back in the BIOS days, installing one bootloader would overwrite the other, but with UEFI multiple bootloaders can be together in one EFI partition. When you remove Ubuntu, just switch back to the Windows bootloader.
    Thanks. That would not be a problem (the GRUB installation behaviour), but, I have had trouble in the past removing GRUB and don't want it to happen again, if possible.

  8. #8
    Join Date
    Jun 2010
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    London, England
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    Hidden!
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    Ubuntu Development Release

    Re: Dualboot WITHOUT Grub??

    You say that in the past you have had trouble with Grub when you removed Ubuntu. Was this is the days of BIOS motherboards? In those days a person needed to re-install the Windows boot loader.

    I do not own a UEFI motherboard computer but I understand that with UEFI the Windows boot files are not overwritten. As stated by Impavidus there is space in the EFI partition for multiple bootloaders and they coexist peacefully. It is certainly a long time since anyone came on this forum and said that they removed Ubuntu and now Windows won't load. Things changed with UEFI and Windows 8 onwards.

    There is one thing that hasn't changed. Windows bootloaders still do not recognise the existence of other operating systems. So, without a Linux bootloader (Grub) you will not be able to load Ubuntu.

    Regards
    Last edited by grahammechanical; October 17th, 2021 at 02:45 PM.
    It is a machine. It is more stupid than we are. It will not stop us from doing stupid things.
    Ubuntu user #33,200. Linux user #530,530


  9. #9
    Join Date
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    Ubuntu

    Re: Dualboot WITHOUT Grub??

    You can manually install Ubuntu in UEFI boot mode to any second drive, but have to manually gpt partition to include an ESP on second drive and do one of several work arounds.
    Ubuntu's Ubiquity installer will only install grub to first drive's ESP. That works fine for one drive or even a second internal drive if second drive always used with same system.
    Just found a page where Apple automatically adds an ESP to every drive as first partition. I have done that since converting to gpt & UEFI.

    Oldfred's workaround during install.
    Posted work around to manually unmount & mount correct ESP during install #55 or( #23 & #26)
    https://bugs.launchpad.net/ubuntu/+s...y/+bug/1396379
    Others suggest disconnecting all other drives physically or logically in UEFI settings, so install drive is first drive.
    Or removing boot flag/esp flag from first drive, so only ESP is install drive. (I have not had that work, but others have.)
    Or if you have ESP on second or external drive, you can just reinstall grub, either manually or using Boot-Repair's advanced mode & full reinstall of grub to correct drive.

    Remove esp flag from Windows before install to second or external drive - Tim Richardson (Also in bug report as workaround)
    Be sure to add ESP flag back to Windows drive's ESP after Ubuntu install.
    https://askubuntu.com/questions/1698...p-disk-creator

    UEFI/gpt partitioning in Advance, new versions use swap file so swap partition optional:
    http://askubuntu.com/questions/74309...-pc-for-ubuntu

    You can also use gparted but must change device label or default partitioning first.
    With gparted select gpt under device, advanced over msdos(MBR) default partitioning before starting.
    300-500 MB efi FAT32 w/boot flag (ESP for UEFI boot or future use for UEFI, you only can have one per drive, so if already existing do not attempt another) as first partition.
    30+ GB Mountpoint / (root) as ext4
    Remaining part of drive /home as ext4
    4 GB Mountpoint swap (optional as default now is swap file) If swap partition put at end of drive.
    UEFI boot install & repair info - Regularly Updated :
    https://ubuntuforums.org/showthread.php?t=2147295
    Please use Thread Tools above first post to change to [Solved] when/if answered completely.

  10. #10
    Join Date
    Jun 2007
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    Arizona U.S.A.
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    5,103

    Re: Dualboot WITHOUT Grub??

    If one drive is NVMe, and the other SATA, then I believe the boot loader location selector will work. The installer default for installing grub now is the ESP of an NVMe drive if there is one, but I do recall choosing the ESP on the SATA drive (which is sda1) as my choice and it was used for this installation. See below: root partition is on a logical volume on the NVMe, and ESP on sda1. (I could have installed root on sda as well, as the OP plans to do, but lose the speedy access.)
    Code:
    dmn@Sydney:~$ space
    Filesystem                        Size  Used Avail Use% Mounted on
    udev                              5.8G     0  5.8G   0% /dev
    tmpfs                             1.2G  1.9M  1.2G   1% /run
    /dev/mapper/sn500_vg-ubuntu_1804   26G   23G  2.1G  92% /
    tmpfs                             5.8G     0  5.8G   0% /dev/shm
    tmpfs                             5.0M  4.0K  5.0M   1% /run/lock
    tmpfs                             5.8G     0  5.8G   0% /sys/fs/cgroup
    /dev/mapper/os_vg2-Common          85G   48G   33G  60% /mnt/Common-Files
    /dev/mapper/sn500_vg-vm_disks     183G  107G   68G  62% /mnt/VM-Disks2
    /dev/sda1                          79M   25M   55M  31% /boot/efi
    tmpfs                             1.2G   24K  1.2G   1% /run/user/1000
    Last edited by Dennis N; October 18th, 2021 at 12:02 PM.

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