Booting linux without bootloader

Question

I installed Ubuntu-Server in Oracle Virtual Machine and it failed grub install step. At the end of install it gave me a message:

You need to manually boot linux
/vmlinuz kernel on partition /dev/sda1 and
root=/dev/sda1 passed as kernel argument

I really wanna know how to boot Linux without a boot loader.

Answer 1

To manually boot linux, you still need to have a bootloader. Normally you just press enter or wait for a timeout, and the default image loads. But you can specify both a kernel image to load and some parameters.

At the grub prompt, type 'vmlinuz root=/dev/sda1' (not sure about the leading / on vmlinuz). The term "manual" means you have to type this stuff manually, rather than letting it automatically boot.

However, since the grub install step failed, it is unclear whether you will ever see a prompt.

Answer 2

Since version 3.3.x, and ONLY on EFI machines, it is possible to boot the Linux kernel without using a bootloader. Have a look at Booting the Linux Kernel without a bootloader.