The instructions are given in a loose chronological order where it is possible to switch around the order in many cases.
Create bootable Ubuntu USB drive
- I used Rufus
- USB drive capacity > 1.6 gb
- Select partition scheme to be the same as the partition that Ubuntu will be installed to
- The partition scheme must also be set to UEFI. Since windows is likely installed with this setting and it must be uniform accros all installation.
- Use FAT32 file system
- Select the Ubuntu disk image
- When asked select iso mod. In case problems araise later use DD mode instead.
- Turn off BitLocker, decryption takes approximately 20 min.
- Use Windows Disk Management to create free space by scrinking the main Windows partition(>100BG)
- Disable secure boot
$ WinKey+R $ shutdown.exe /r /o /f /t 00
- Select Troubleshoot->UEFI Firmware Settings
- In BIOS, disable Security->Secure Boot and set Startup->UEFI/Legacy Boot to UEFI only
- (optional) set Boot Mode to Diagnostics
- Press F12 during boot
- Boot from the USB drive
- Create a ext4 partition from the free disk space
- Use root(/) as mounting point
- Select partition with windows bootloader(efi) to install linux bootloader, usually 2nd partition
- Press F1 during boot to enter BIOS
- Change boot order under Startup->Boot so that ubuntu is at the top
- Costomize the grub boot order GUI or commandline
- Enable Bitlocker and backup the new recovery key
- Revert various changes in BIOS
- Enable "Secure Boot"