Ubuntu – Dual booting in CSM mode

uefiwindows 8

CSM boot mode does not detect windows 8 as being installed but it's the only way I can boot any version of Linux. Will windows 7 install in CSM so i can install ubuntu for dual boot purposes?

Best Answer

It is vital for all systems running Windows 8 in UEFI mode to have fast boot and hibernated shutdown turned off, as well as fast boot in the UEFI. This keeps you from losing data on your Windows install.

I feel like I keep giving this same answer over and over again, but c'est la vie:

First off, you cannot run dual boot configuration with Windows 8 in UEFI and any *nix in CSM. Grub will not be able to see the Windows 8 installation (in my experience). Either way:

If you want Ubuntu on the same disk as Windows 8.1, here are the steps to go through:

1) Turn off Windows Fast Boot

2) You need to shrink the main Windows 8.1 partition. This can be tricky, as Windows expects a certain partition scheme to be used. Let me show you a diagram:

[(Windows RE Tools)(EFI System Partition)(Microsoft Reserved Partition)(Windows 8.1)(Anything else)]

You can use your favorite tool to edit these partitions. I prefer Gparted, but any good disk partitioning tool can handle this. Backup your Windows install first. Then, resize the Windows 8.1 partition so that you have enough space for another OS. I prefer to give my Linux installs about 50-100 GB of space (for expandability).

3) Download your Ubuntu (use 64 bit only and I suggest 13.10) iso and put it on some media (CD/DVD/USB/(insert your preferred media here)) by using your favorite tool (most people prefer Rufus) or dd.

4) Shut off Secure Boot and Fast Boot in the UEFI. DO NOT TURN ON LEGACY BOOTING (if your motherboard supports UEFI only booting without Secure Boot and Fast Boot on.)

5) Insert your install media and install Ubuntu in the partition you made earlier. Make sure that for your EFI boot partition, you make the installer use the EFI System Partition already created by Windows 8.1. The partition should be something like sdXn (replace X with the drive it is on and n with the partition number, such as /dev/sda2), but this could be different. DO NOT REFORMAT THIS PARTITION!! You are only going to tell the installer to use it as the EFI partition. It will put the grubx64.efi bootloader for Ubuntu in this location.

6) With that done, continue the install as normal and set up your partitions as you see fit. Once the install is finished, you should be able to boot into Jessie easily.

If you are trying to fix an existing install of Ubuntu, you will need to do:

sudo apt-get install grub-efi-amd64

sudo modprobe efivars

sudo grub-install /dev/sdx (x being the drive Ubuntu is installed on)

sudo update-grub

From there, the UEFI should use Grub-EFI as the bootloader. I have not found a way to get the Windows 8 bootloader to see and allow Linux to boot in UEFI. YYMV.