grub2 - How to dual-boot Ubuntu + Windows 8 on a Samsung Series 9 laptop?

I have a Samsung Np900X4C which came with Windows 8 installed.

My goal is to have a dual-boot setup. I followed pretty much the answer at Samsung series 9 np900x4c-a03us Dual boot windows 7, namely:

1. Disabled secured boot in BIOS


2. Changed "OS mode selection" to CSM OS*


3. Booted from the USB and installed Ubuntu 12.10

*- with UEFI + CSM OS I got some kernel panic errors while booting from the USB

The problem - I can only dual boot if I change the boot type in the BIOS:

1. With CSM only I get the Grub options and I can boot in Ubuntu. If I select the Windows 8 option I get a windows error message** and can't boot.


2. With CSM + UEFI OS or UEFI only I boot straight into Windows 8

**- windows boot manager - Windows failed to start(...). The boot configuration data for your PC is missing or contains errors.

It seems like I have the traditional grub installed and UEFI boot installed and I can't have both working simultaneously.
How can I correct this dual-boot setup? If I did install Ubuntu on legacy BIOS and shouldn't have, how do I correct that?

You did install Ubuntu using the BIOS/legacy boot option -- that's what "CSM" is. (This acronym expands to "Compatibility Support Module," which is EFI-speak for BIOS compatibility mode.) Thus, setting the "OS mode selection" in your firmware to "CSM" for the installation essentially tells your computer to boot only in BIOS/legacy mode.

There are a number of possible solutions. These include:

• Install my rEFInd boot manager in Windows. Edit the refind.conf file: Uncomment the scanfor line and add hdbios to its options. When you reboot, rEFInd should come up and show at least two boot options. One should boot Windows and the other should start up GRUB in BIOS mode, which should in turn launch Linux. If you try this and want to experiment more, you could try tweaking the configuration to boot Linux directly in EFI mode.


• Convert your existing Ubuntu installation to boot in EFI mode by adding a suitable EFI-mode boot loader. rEFInd can serve this purpose, or you could install ELILO or the EFI version of GRUB 2. The trick is registering the EFI boot loader with the firmware, which requires an EFI-mode boot of Linux or doing the work from Windows. (The preceding option does this for rEFInd by doing the work in Windows.) See my EFI Boot Loaders for Linux site for more on your options on this score. This approach has a fairly steep learning curve, but it's a fairly clean approach. There's the caveat about EFI-mode boots possibly having problems on your system, though.


• Re-install Ubuntu in EFI mode. This will require overcoming your kernel panic problem, though, and I don't have any specific suggestions on doing that. Perhaps adding (or removing) a kernel option would do the trick, or switching to another kernel version (but this is awkward for an installer's kernel).

Overall, I'd say your easiest course of action is to install rEFInd. It will probably enable you to boot Linux in EFI mode, and it provides a path to experiment with EFI-mode booting if you decide to pursue that.