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I have two computers, this one runs Windows 10. I removed the Ubuntu disk from another computer and plugged in this one. The BIOS can detect the ubuntu drive, but didn't list it as bootable.

I want to be able to boot into ubuntu and windows. I think I have to add an entry to the Windows 10 EFI partition, in that partition there's a /EFI/bootx64.efi, and I'm wondering where's the equivalent for that in my ubuntu disk, and I don't know where I should put it. Should it be named /EFI/Ubuntu/bootx64.efi or what?

(I'm using DiskInternals Linux Reader to access my Linux partition at the moment.)

Razor Rassh
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seilgu
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  • Welcome to AskUbuntu! Does the Ubuntu disk also have an EFI partition? or was it installed in BIOS mode? Please [edit] the output of lsblk -f | grep -v squashfs into your post. Thank you for helping us help you! – Elder Geek Jul 27 '19 at 19:20
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    External drives only boot in UEFI mode from /EFI/Boot/bootx64.efi. That file can be Windows or Linux. Now internal drives may also have that file as fallback or emergency boot. A few systems have used that as the default internal drive boot using a copy of Windows boot file. Usually best to have boot files on same drive as install. But Ubiquity installer with Ubuntu only installs grub to first drive's ESP - efi system partition by default. Boot-Repair may let you reinstall grub to new drive. https://help.ubuntu.com/community/Boot-Repair – oldfred Jul 27 '19 at 20:10

2 Answers2

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You have to set the BIOS to "Enable Legacy Boot options". It sounds like the bios is only set for EFI at the moment which uses GPT and legacy boot uses MBR. Once you have set the BIOS to allow for legacy boot then you should be able to boot it. You don't have to do anything to the disk itself. IF ANYTHING you would have to go into the bios and add the boot option for the disk by pointing to the /EFI/Ubuntu/bootx64.efi or whatever the file would be.

Gordster
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Use sudo gparted and this screen shows up:

gparted 1.png

From the menu pick GParted -> Devices -> /dev/sda (or whatever your hard disk is called).

Then gparted refreshes with the other drive's partitions. In my case like this:

gparted 2.png

Note: This 1 TB hard disk has 919 GB usable. Only 42 GB is used because when it was a brand new laptop and the first thing I did was put in an SSD and never used Windows 10 on the hard disk. I plan to use it for backups someday.

Now select Partition->Manage flags and this dialog box appears:

gparted 3.png

Check the box next to boot flag.

WinEunuuchs2Unix
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