I did manage to install ubuntu onto my Vizio laptop with Windows 8 after changing the following settings in the Setup:
- Security -> Boot -> Secure boot -> Disabled
- Advanced -> OS support -> Other OS
- Boot -> UEFI -> USB key first
Ubuntu was installed successfully, I was able to boot without any problem. However to boot Windows I needed to enter Setup again and select Security -> Boot -> Secure boot -> Enabled.
Since I wanted to have entries for both Windows and Ubuntu I decided to run Boot Repair. I ran it with "Secure boot" checked (from Ubuntu which was running with the "Secure boot" disabled option). Other options were left by default. I wasn't able to boot Windows and Ubuntu after restarting.
I booted using my bootable flash drive and run Boot Repair again. But now with the "Secure boot" unchecked. After rebooting I get grub with both Ubuntu and Windows. They both boot successfully. The only problem is that now if I choose Security -> Boot -> Secure boot -> Enabled in the Setup, I get the following error:
Secure boot violation
Invalid signature detected. Check secure boot policy in setup.
I must admit that I'm new to UEFI. I don't understand how to make Secure boot working. By the way is it really needed?