How to install Ubuntu 20.04 desktop alongside Windows 10 as dual boot

Question

I tried to install Ubuntu 20.04 desktop on my laptop after having already installed Windows 10 Home edition, the latest version available yesterday (and updated to that date) January 20 2021. I succeeded in doing so, choosing Minimal Installation with Download updates while installing Ubuntu. Then choosing Something else choosing a partition that I prepared to receive the Ubuntu installation.

According to GParted the disk layout is as follows:

/dev/sda
   Free space 1MB
   sda1 fat32 104MB, used 33MB (partition was automatically installed during Windows installation)
   sda2 ext4 16MB, unknown how much space used.
      (partition was automatically installed during Windows installation)
   sda3 ntfs 52429MB Windows operating system, unknown how much space used
   sda4 ntfs 524MB, used 431MB Automatic created during Windows installation)
   sda5 ext4 202982MB, 11859MB used, Ubuntu 20.04
   Free space 1MB

I prepared sda5 as ext4 journaling file system, mount point /

Before continuing I got the message “No EFI System partition was found. The system will likely not be able to boot successfully, and the installation process may fail. Please go back and add an EFI system partition, or continue at your own risk". I didn't know whether I could set one of the existing partitions as an EFI System partition. Could I set sda1 or sda2 or do I have to make some free space and create a new partition?

As I continued ignoring the screen message (at my own risk) Ubuntu seemed to be installed well, but I can only boot Windows.

Windows sees the disk layout as follows:

   HD0: 238.46GB
   E: 100MB FAT, filesystem
   C: 48.83GB NTFS starting disk, buffer file and crashdump
   partition 4, standard, recovery partition
   partition 5, Primary partition <--this must be the Ubuntu partition

I think I have to redo the Ubuntu installation and leave Windows untouched. Is that correct? What can I do in order to get a dual boot system after Ubuntu installation? Could I set sda1 or sda2 as UEFI System partition in order to solve the problem?

Answer 1

As I look through the different partitions listed by you, I'm sure the Windows 10 was installed using Legacy Boot Mode. You can't make UEFI dual boot in this setup unless you re-partition and install Window 10 using UEFI mode. If you don't want to touch the Windows 10 installation, you need to continue with the current partitions and install Ubuntu in Legacy Boot Mode. You selected unknowingly UEFI boot while booting from USB. Repeat the installation steps you followed using Legacy Boot Mode. You'll need to search google for the steps in doing so for the system brand and model you own. Hope this makes sense but if you need further clarification, do comment with the system brand and model number so that we may help you further.

One more thing to remember is that you need to disable 'secure boot' if it is enabled.

Good luck!

Answer 2

I have assigned partition sda1 to be EFI System Partition during the installation process and now GRUB works. During startup I can now choose between Ubuntu, Advanced options for Ubuntu, Windows boot manager (on /dev/sda1), and UEFI Firmware Settings. Problem solved!

Answer 3

I think you can try to turn UEFI on before installing ubuntu. just by hitting f12 on the reboot. after that u can perform the installion normally and when u come to disk type step window another option Dual boot alongside windows 10 will show up.