Score:0

Dual-boot straight to Windows 10 (MBR Legacy Bios)

pt flag

I see lots of questions and answers regarding dual boot but all relating to UEFI...

I've just installed Ubuntu 20.04 over Win 10 with MBR partitioning and Legacy bios. (I've used Rufus to create installation with settings set accordingly).

I've tested Ubuntu and it worked okay, so I installed it. However, after restart it starts straight into Windows 10. I've disabled Hibernation and Fast-start but to no effect...

Is there any solution allowing to run Dual-Boot on Legacy Bios with MBR?

Thanks!

guiverc avatar
cn flag
I don't understand how `rufus` relates; it's purpose is to create installation media; not do the actual install (Ubuntu 20.04 LTS desktop installer is `ubiquity`; Ubuntu 20.04 LTS Server installer `subiquity` etc... which is run from the `rufus` created media for the actual installation). It reads to me like you created installation media, and haven't yet booted & installed it yet. My box is dual boot, using MBR & I have no issues; MBR & *legacy* I find easier than uEFI systems as they're more consistent (uEFI seem to be more firmware specific for consumer devices with strange quirks)
pt flag
Thanks. What I meant with Rufus is I wanted to confirm that I've created the installation USB correctly (I saw that usual answers are that someone tried to install over MBR etc...) I've booted through the usb and installed UBUNTU and after that it asked me to remove USB drive and re-start comupter. And it boots straight into Windows 10
oldfred avatar
cn flag
Be sure to make a Windows repair/recovery flash drive or have the Windows installer with repair tools. And Ubuntu live installer. With MBR, you only have one MBR and then only one boot loader. But grub only boots working Windows and then you have to temporarily restore Windows boot loader, fix Windows and restore grub. UEFI, in effect ,is like having multiple MBRs for boot loaders. Windows will turn fast start up which sets hibernation flag, with updates & then grub will not boot it. It the NTFS may need chkdsk & grub will not boot Windows. If you have two drives, best to use both MBRs.
ChanganAuto avatar
us flag
@guiverc Whenever you "burn" the ISO with any tool running DD underneath it creates a 1:1 copy that can boot either way. But Rufus has a different philosophy according to their authors so by default it extract one bootloader or the other depending on the user selections (BIOS/MBR and UEFI/GPT). It can do DD as well but that isn't the default option. The OP is correct in mentioning how it done (with Rufus) so there's no doubt it indeed booted and installed in the intended mode. Why that was the intended mode it beats me, unless the target is actually BIOS.
Score:2
us flag

Legacy MBR boot should be using grub. When I've had problems with this in the past the best method for fixing it was to boot from the live media, in this case your USB media probably has this option, and then run Boot-Repair.

There are some instructions for using Boot-Repair here: https://help.ubuntu.com/community/Boot-Repair

There are also ways of repairing grub manually, but I think this is the direction you want to go.

Score:0
eg flag

I conclude from this when you made your installation-device with 'Rufus' it was set to 'MBR' and not to 'GPT'. Also assuming that you can see your partition in Windows diskmanager.

You can boot from your installation-usb to do a boot-repair ( see the answer from Habadeer )

You can use 'Grub to disk' or 'Ikki Boot' to find your Ubuntu installation, start it up and then repair it. ( This is why I love Ventoy, install it on your usb-stick and drag 'n drop multiple iso's to it, which are all bootable ).

You can install 'GrubforWin' in Windows, and use that. ( Not as stable as the normal grub2 though. It always messes with my advanced Mint options. I run win 10, Kubuntu and Mint.)

Once booted check your 'grub'-file in /etc/default/ to see if your 'GRUB_TIMEOUT' is set correctly ( standard is 30 ( time in seconds )).enter image description here

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