Why do I need to create a bios-grub partition when I install 12.04?

Question

Is the bios-grub partition in Ubuntu 12.04 mandatory?

I have used 11.04, 11.10 and 12.04, But I was never asked for this.

Today I tried a fresh installation of Ubuntu 12.04 and for the first time I was asked for this Grub partition of minimum 1Mb. I first tried to reinstall 12.04, but the error continued.

So I installed Fedora 16, Keeping all partitions as they were (replaced Ubuntu with Fedora), And then did another fresh installation of 12.04.

Is it ok to continue with this grub partition or is there a fault in my system's hardware? If this is a (hardware) fault, how can I fix it?

I'm using a Lenovo S10-2 Ideapad. The only OS right now installed is Ubuntu 12.04.

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well, let me answer. It was /usr/bin/xorg issue that I had with firstly installed precise. I used fedora16 basically for removing precise totally (my experience tells me ubuntu can't completely erase and reinstall by itself). this 1mb grub is created by fedora. I then wanted to remove it while reinstalling ubuntu but got caution bootloader may fail. hence I have to keep this 1mb drive. but prior to yesterday, i used both fedora and ubuntu, even same CDs, but had no such partition. my question is if this partition is necessary or not? if not, how can i safely remove it from my system?

Am using only ubuntu 12.04 -- before and after (now).

Solution

The GUID Partition Table (GPT) is a way of partitioning disks that's more flexible than the older Master Boot Record (MBR) system. GPT works on bigger disks than MBR (which has a 2 TiB limit, assuming a standard 512-byte sector size) and it has some other minor advantages. When GRUB 2 installs to a GPT disk on a BIOS-based computer, it likes to have a BIOS Boot Partition in place, and this is what Ubuntu's installer means by the "bios-grub" partition. This is basically a small partition in which part of GRUB's code resides. It's not needed on MBR-based computers because GRUB 2 uses some officially-unallocated space instead. The GPT method is actually safer, but the MBR method usually works, in practice.

I suspect that this is what happened:

1. In previous installations, you used GRUB 2 on MBR disks and so had no need of a BIOS Boot Partition.
2. When you installed Fedora, it converted a blank disk to GPT format. Fedora 16 is known to do this; it favors GPT even when it's not strictly necessary. (The Fedora developers are reportedly reversing this decision for Fedora 17.)
3. When you tried to re-install Ubuntu, it saw the GPT configuration and tried to use it. This involved creating a BIOS Boot Partition, or complaining if one wasn't present.

There's absolutely no harm to using a BIOS Boot Partition. One of GPT's advantages over MBR is that GPT doesn't have a 4-primary-partition limit, so devoting 1 MiB of space to a BIOS Boot Partition doesn't chew up precious partition resources. In fact, using GPT has some minor advantages, such as a lack of distinction between primary, extended, and logical partitions (you can create up to 128 partitions by default) and the use of backup data structures and CRCs to help protect against accidental destruction of your partitions. That said, if you want to dual-boot with Windows, using GPT will prevent installing Windows unless the computer has UEFI, rather than BIOS, firmware. This is a big minus. There are also buggy BIOSes out there that won't boot from GPT disks unless you jump through some extra hoops.

If you want to install to an MBR disk, you'll have to remove the GPT data. You can do this with GParted by selecting Device -> Create Partition Table. Be sure that you opt to create an "msdos" partition table (what GParted calls MBR). This will wipe the GPT data and convert to MBR. If you have data you want to preserve, you may be able to do a GPT-to-MBR conversion with my gdisk program, but this doesn't always work. Also, converting in this way will render the disk unbootable until you re-install your boot loader.

Comments

[Takkat]

Did you install UEFI BIOS?