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I have been struggling to install ubuntu 13.04 on windows 8. because of UEFI, no existing ways (wubi, etc.) does not work and installing grub2 on the boot is a real pain.

I see on the BIOS menu that it has legacy support and says

"BIOS will load Compatibility Support Module (CSM) to support legacy OS such as Windows 7...".

If I enable that option, will windows 8 continue working as CSM will replace UEFI? and will wubi work to make PC dual boot as CSM will be on place??

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up vote 2 down vote accepted

If you put your computer into CSM mode then you will have to reinstall Windows 8. CSM makes the computer boot with a BIOS and non-CSM boots with UEFI. The way the hard-disks are laid out (MBR, and GPT) are different with each mode and that is why they are incompatible. Ubuntu's wiki item (shim bootloader with Microsoft key) provides the best advice for your situation.

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Actually, the linkage of MBR with BIOS and GPT with EFI is more of a Microsoft issue than anything else. Linux is happy to boot from a GPT disk in BIOS mode or from an MBR disk in EFI mode (although some EFIs may limit booting from MBR disks; I haven't really looked into this in detail). – Rod Smith Aug 11 '13 at 4:17

WUBI has always been a second-best method of installing Linux, even in BIOS mode, so its incompatibility with EFI-mode booting is no great loss, IMHO. WUBI's greatest strength is that it enables installation without modifying existing partitions, and that can be done as well, if not better, via virtualization technologies like VMware or VirtualBox.

Rather than try to cram the square peg of WUBI into the round hole of EFI (even with CSM active), I recommend you work on getting Linux booting in EFI mode via a more traditional dual-boot configuration. Although there are numerous known problems with EFI-booting Linux, they all apply to small numbers of systems and/or have easy fixes, such as disabling Secure Boot. You haven't provided any details about what problems you've encountered, so it's impossible to give you any real advice, except perhaps to take the scattershot approach of listing some of the more common problems and associated solutions. I don't see any questions from you on this site about EFI installation other than this one, so I recommend you review some existing questions and other Web sites, and if you still have problems, post a new question. Some existing questions and other sites that may be helpful include:

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