I have a Dell Latitude 3590 with Windows 10 installed as factory setting. I previously installed ubuntu 18.04.2-desktop with an iso image on a usb drive with dual boot allowing me to choose between ubuntu and windows 10. For various reasons, I wanted to reinstall ubuntu 18.02.4 as brand new. In doing so, I chose "delete ubuntu and reinstall" (or something like that during reinstallation) and something failed at the very end of the installation. Ubuntu opened, but since I restarted, I can't access it again. When I turn the PC on, it tries to boot on ubuntu, but ends up with "GNU Grub 2.0" as a command line. When I get in the Bios, I can either boot ubuntu (which gets me back to grub) or windows, or a usb drive in legacy mode. I cannot boot a live ubuntu version either, because I don't get that option : trying to boot from a usb drive with ubuntu on it gets me directly to grub without asking what kind of installation I want for ubuntu.
I would like to be back to my intial state, which was dual boot between ubuntu and windows.
My main hard drive is partitioned as follows :
-a 650 Mo partition labelled "Healthy : Partition of EFI system" -OS (C:) which is the main partition with windows 10 on it (442 Go NFTS)
- another partition with 450 Go on it labelled as "main partition", which is supposed to have ubuntu on it since it's the space I allowed for ubuntu in the first place
-the WINRETOOLS partition (990 Mo NFTS), labelled "healthy - OES partition" (I don't know what it means).
I have tried :
-putting super_grub2_disk ISO image on a usb drive in order to restore grub. After some more or less random errands, i learned that the partitions sizes appear to "not match". I tried use it to install /dev/sda5 (where the ubuntu partition appears to be), but got errors. When i exited it, it made ubuntu boot, but that doesn't solve the booting problem, I would like to have a proper dual boot and not have to dot that every time I want to boot ubuntu.
-putting boot_repair_disk ISO image on USB drive to try to repair it. However, I can only boot from a USB drive in legacy mode, and this appears to prevent any action. It tells me that I need too boot the USB drive in EFI mode, which I apparently cannot.
- delete or format the 3rd partition which is supposed to have ubuntu on it (I've been led to understand that I can't reinstall ubuntu due to the information related to the partitions) in order to reinstall it from scratch. I wasn't allowed to do it by windows, nor from partition manager, nor from diskpart, nor through the registry with regedit.