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What is the BIOS boot area and do i need it. I have a bare new drive and I plan on resorting back to dual-booting windows. I had re-re-installed Ubuntu and windows several time and it did not work. I would only get windows to boot or a error message saying "please install a operating software media"

So looking into the installer, i found this "BIOS boot area" I have no idea what this dose or if i need it (yes I've done research on what it dose, but not in full detail nor do I understand it). So do I need to use "BIOS boot area" for dual boot and do I half to install windows on the PC first before Ubuntu??

weezle1234
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  • What version of Windows? And do you want UEFI boot or BIOS boot? And what brand/model system? Windows only boots from gpt with UEFI, and only with BIOS from MBR(msdos). And Windows 7 defaults to BIOS, unless you copy to flash drive and reconfigure. But Ubuntu can boot from gpt partitioned drive with BIOS if you have bios_grub partition, or with UEFI if you have the ESP - efi system partition. How you install Windows, UEFI or BIOS, is then how you install Ubuntu. But once drive is gpt, Windows may convert incorrectly to MBR and you will have issues. – oldfred Oct 02 '15 at 21:03
  • Windows 7, the bios is uefi, however, it dose have the "legacy mode" with two uefi settings. This problem also occurs when I DO have windows installed and the Ubuntu installer dose not recognize windows existence. – weezle1234 Oct 02 '15 at 23:08

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It's unclear precisely what the "BIOS boot area" to which you refer is. Two possibilities spring to mind:

  • The Master Boot Record's (MBR's) boot code -- The MBR is simply the first sector of the hard disk. It holds both the first stage of the BIOS boot loader and the MBR partition table. When a BIOS-based computer boots, it reads the MBR and executes whatever code it finds there. The same thing happens with an EFI-based computer with its Compatibility Support Module (CSM; aka "legacy support") active and in control of the boot process. If no executable code is in the MBR, the computer is likely to lock up, possibly with a message like the one you've described; but details vary from one computer to another.
  • The BIOS Boot Partition -- This is a type of partition that can be present on GUID Partition Table (GPT) disks that holds the second stage of GRUB 2. If it's not present, GRUB 2 will refuse to install to such disks unless you pass it an override option, in which case GRUB's second stage goes in a filesystem. If GRUB is installed but then the BIOS Boot Partition is damaged, the boot will fail. I don't recall offhand if you'll see any error messages in this case.

Backing up a bit, Rule Number One when dual-booting is to install both your OSes in the same boot mode -- BIOS/CSM/legacy or EFI/UEFI. If you install one OS in BIOS mode and the other in EFI mode, you'll have to jump through extra hoops to get it to work. The result is usually awkward at best. Sometimes it's impossible; it depends on the firmware and OSes.

If you install Windows, the boot mode dictates the partition table type (MBR or GPT) -- Windows insists on having an MBR for a BIOS-mode boot and GPT for an EFI-mode boot. Linux is more flexible, but there are sometimes problems with BIOS/GPT and EFI/MBR combinations, so they're best avoided if at all possible. In sum, your choice of boot mode and partition table are tied together. Depending on your firmware and hardware (disk size), you may want to pick your boot mode and set your partition table type appropriately or pick your partition table type and set your boot mode to match. You've presented no information that would help me give more specific advice; however, as a general rule, EFI-mode booting is best on modern computers, since activating the CSM complicates the boot path, which makes controlling and debugging the boot process harder. See this page of mine for more on this subject. You may also want to read the following pages for more on EFI-mode booting:

Rod Smith
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