Ubuntu – I cannot re-install Ubuntu 15.04 alongside windows 8.1


This question may seem repeated but I have other more issues.
I installed 8.1 in my dell 5537 and dual booted it with ubuntu 14.04..I worked well..I installed with alongside windows option..It took 30gb(as I selected the space) space from my logical drive which was last drive…I have four partitions c:,D:,E:,F:(or local drives). Now I deleted the ubuntu from disk management(as there was some problem in ubuntu and i could not fix it).I fixed the windows MBR with live CD. I now want to dual boot ubuntu 15.04 again..I have changed boot mode to UEFI(with secure mode disabled) I get grub to install ubuntu. I clicked install ubuntu. Now i get the Message of

"force UEFI installation?…this machine's firm ware has started the installer in UEFI modebut it looks like there may exist operating systems already installed using "BIOS compatibility mode"…If you wish to install in UEFI mode and dont care about keeping the ability to boot one of the existing system,you have the option to force that here……".

Now if i force UEFI i cannot see any of my partitions of windows and see my whole disk as 500gb disk(as /dev/sda ntfs) and no option of new partition table or other disk…It will erase my whole disk…..I have already shrinked volume from C: and divided that space into 3 part (one primary and active ,two logical).

I use mostly windows and don't want to lose any data from any disk and volumes..
I am not familiar with linux much…So please help with detailed steps…

Best Answer

First, you need to be aware that there are two methods of booting most modern computers:

  • BIOS/CSM/legacy mode -- This mode is what was used on most computers prior to about 2011. It uses either an old-style BIOS firmware or BIOS emulation ("CSM" or "legacy") on a more modern firmware. It's usually paired with an MBR partition table. Note that on a modern computer, BIOS/CSM/legacy mode is the non-native boot mode; using it is like using WINE to run Windows programs in Linux.
  • EFI/UEFI mode -- Modern firmware uses the Extensible Firmware Interface (EFI) or its 2.x variant, UEFI. UEFI-mode booting is completely different from BIOS-mode booting and almost always uses a GUID Partition Table (GPT). Unfortunately, there's a lot of misinformation and bad advice about EFI-mode booting, which is making the transition from BIOS to EFI harder than it should be.

I strongly recommend you read up on these subjects. The Wikipedia articles referenced above are a start, although they're a bit dry and divorced from practical concerns. Three others you might read are:

It sounds like you've converted from an EFI/GPT setup to a BIOS/MBR setup, but you did so with a tool that does an incomplete GPT-to-MBR conversion. Thus, you're not really using your EFI/UEFI firmware as such, so the preceding references may seem of only peripheral interest -- but your firmware is an EFI, not a BIOS, and this fact means that you're dealing with EFI issues even when you boot in BIOS/CSM/legacy mode. If I'm right, the fix to your specific problem is to use FixParts (part of the gdisk package in Ubuntu) to remove the stray GPT data. See here for more information:

Unable to recognize and create partitions for Ubuntu Installation on Dell Inspiron 15R 5520

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