I had a dual booted system with Windows and Ubuntu. I wanted to remove Windows so I deleted all the Windows partitions (Even the System Reserve) which in retrospect I shouldn't have(?). So now when I try to boot I get the following message :

BootDevice Not Found. Please Install an Operating System on your Hard disk Hard Disk - (3F0)

When I ran boot-repair I got:

The boot of your PC is in EFI mode, but no EFI partition was detected. You may want to retry after creating a EFI partition (FAT32, 100MB-250MB, start of the disk, boot flag)

What I am thinking now is to move the sda5 by around 200Mb and make an EFI partition there. Would that help?

Current state of my partitions enter image description here

  • @PRATAP Thanks a ton for helping. Could you explain to me what exactly is the problem? Was grub on the system reserve partition that I wrongfully deleted? Nov 2 '18 at 17:05
  • @PRATAP Sorry but I am a novice at this. Does changing boot mode to BIOS mean legacy boot mode? Nov 2 '18 at 17:11
  • @PRATAP I checked my boot configuration and under the option Configure Legacy Support and Secure Boot there was Legacy Support Enable and Secure Boot Disable. I guess this means Legacy Boot mode is enabled? If not how should I go about doing that. (HP Laptop) Nov 2 '18 at 17:26
  • I don't remember. It's been a very long time. But the results of boot-repair indicate that the boot is in EFI mode right? I had windows 10 and I am not sure about the boot mode but I think it was EFI. Nov 2 '18 at 17:30
  • Let us continue this discussion in chat. Nov 2 '18 at 17:36

The problem was that I had removed that partition that had my Grub. Hence to solve it I made an EFI System Partition.

This excellent answer explains how to do that.

Also after this was done I had to change the boot options of my System to use UEFI instead of Legacy.

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