I installed Ubuntu 18.10 on a laptop. When I opened Gparted I saw this little partition and do not know what it is (see image). Gparted also has a warning about it:

Unable to read the contents of this file system! Because of this some operations may be unavailable. The cause might be a missing software package. The following list of software packages is required for fat32 file system support: dosfstools, mtools.

fdisk has it as:

/dev/nvme0n1p1    2048       6143       4096     2M BIOS boot

What is this partition, why is it there and do I need it? I have never noticed such a partition before.

Update: I find this hard to understand even after having read up on it. I add my disk layout here:

sudo parted -l /dev/sda
Model: SAMSUNG MZSLW1T0HMLH-000L1 (nvme)
Disk /dev/nvme0n1: 1024GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags: 

Number  Start   End     Size    File system  Name  Flags
 1      1049kB  3146kB  2097kB  fat32              bios_grub
 2      3146kB  543MB   540MB   fat32              boot, esp
 3      543MB   1024GB  1024GB  btrfs

I guess I have a gpt partition so therefore I have the bios_grub partition? This is a relatively new install of 18.10 and I wonder why the partition table is gpt?

Gparted screenshot

  • This is created to boot from bios a gpt disk – Pilot6 Mar 5 '19 at 20:50
  • The bios_grub partition has to be unformatted and 1 or 2MB, and the ESP - efi system partition needs to be 100MB to 500MB and FAT32. So not sure what your partition is. – oldfred Mar 5 '19 at 21:04
  • I still wonder why gparted sees this partition on this install of Ubuntu? I have never seen it listed in gparted before on any install. I do have a 515 MB /efi partition also. – Christian Mar 5 '19 at 21:08

BIOS mode

  • I think you had drives with the MSDOS partition table before. Such drives do not need a bios_grub partition. Instead part of grub is written into the head of the drive (between 512 B and 1 MiB) in order to boot in BIOS mode (alias CSM alias legacy mode).

  • If there is a GUID partition table, GPT, you need a small partition with the bios_grub flag (for the corresponding grub data) in order to boot in BIOS mode (alias CSM alias legacy mode).

I think the reason why you see a partition with the bios_grub flag is that you have installed an operating system in BIOS mode, and the installer created that partition for you.

UEFI mode

  • With both kinds of partition tables you need an EFI system partition in order to boot in UEFI mode.


See more details at this link, help.ubuntu.com/community/DiskSpace

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