I was dual-booting Windows 10 and Elementary OS then decided to change Elementary OS to Deepin OS.
The following was my reinstall procedure:
○ Booted into my deepin installation pen drive In the Deepin disk selection screen:
○ Deleted the partition containing Elementary OS (I did not make any separate partition when I first installed Elementary OS)
○ Installed the / (root) partition on that partition I deleted.
○ Started installation. There was no error prompted during or after the installation.
○ Reboot (as deepin was telling to do)
○ Then the system did not show any grub menu… neither did it take me to any of my os (Windows and newly “created” Deepin OS)
Instead the system took me to the device boot manager of the BIOS.
So now I am stuck with no OS since I cannot access windows nor linux.
What can I do to fix things up?
NB : I did plug the host disk to another computer and the windows partitions could be accessed properly.
Try all the boot disks proposed in the boot menu. There is a high chance one of them will be booting into GRUB, just fine.
If it still does not work, then I suppose the easiest way is to make sure that GRUB is installed properly, by e.g. re-installing Deepin and making sure it actually installs GRUB correctly.
Additionally, if you are on a UEFI system, then you need an EFI partition, which is always separate from the root partition. So if you only created the latter, the boot won’t work, as you are experiencing right now.
Sometimes, there is an option to boot from the USB drive in UEFI mode, too. Look out for that option. Sometimes this option does not appear, if the ISO isn’t burned the right way onto the USB drive.
To fix the last proposal, you need to boot into Windows by selecting the Windows Boot Manager in the boot menu in the UEFI, get Rufus and burn the disk in UEFI and DD mode. Then try again.
Welcome to It’s Foss @Fogasy. This sounds very similar to me when I was experiencing with different installs (Distro) of Linux. I am pretty sure the problem (for me) was Linx installed in a EFI partition and Win 10 was installed in MBR format. The PC would not boot. I’m pretty sure EFI and MBR are not compatible.
My solution was to restore my Win 10 partition. Not much help.
I hope you have a backup of your PC and can restore your 2 OS’s. In this computer age, you have to have a backup of your system.
I supposed that it was a grub issue, as what maybe the initial grub config got messed up on the linux os replacement installation. So I used a live session of Linux Mint to go for a boot repair. Unfortunately, it did not fix my problems.
Then I checked how the partition I installed the OS’s on were doing. For that I used Super Grub2 Disk to manually boot to my systems. Super Grub2 could detect all the OS and I could boot manually into them (Windows and Deepin) with no problem. So the disk is definitely not failed as opposed to what boot menu says. This clears up the need of reinstalling anything since installation is alright…
Then went to Windows and made a disk check hoping that windows auto scan and repair could find any fault and resolve it… but, still no result (just a long wait).
From there I oriented myself to boot record issues. So I did boot to WinPE and did apply the following procedures : bootrec /fixmbr > bootrec /fixboot > bootrec /rebuildbcd /fixmbr was successful but /fixboot and /rebuildbcd threw Element not found error.
So current state of my situation is : the two os of my dual-boot sys are fine but I have no “interface” to allow me from accessing them when I boot my PC. The best would be that I don’t end up reinstalling everything from scratch… since my Windows environment has lots of programs already installed!
Most probably Grub is not installed correctly to efi partition. I suppose elementary OS didn’t have grub, but systemd stack. You have to use the live iso and then mount the system partition (Deepin) and the efi partition and chroot into it to reinstall grub, then update grub. Deepin doesn’t have a live iso, but you can get it running as live to use it to do the job. (When booting Deepin, ALT-F2. Then change with LANG=EN_en.utf8 startx) Or use another live iso.