Quickly Check If Linux System is Using BIOS or UEFI

Is your Linux system in BIOS or UEFI mode? Don’t worry, this guide will show you quick ways to check if Linux system is using BIOS or UEFI. BIOS (Basic Input/Output System) or UEFI (Unified Extensible Firmware Interface) are two different firmware interfaces that are used to boot up a computer. BIOS is the older interface, while UEFI is the newer interface. Most modern computers use UEFI, but some older computers may still be using BIOS.

Checking If Linux System is Using BIOS or UEFI

So, how can you know if Linux system is using BIOS or UEFI?

Check the /sys/firmware/efi directory

From the Linux terminal, run the command below to check if the /sys/firmware/efi is present on your system.

ls -d /sys/firmware/efi

This directory is usually only present in the systems using UEFI. Therefore, if it exists, it means your system is using UEFI. Otherwise, it’s likely using BIOS.

See sample output from two different systems;

System using BIOS;

ls -d /sys/firmware/efi

ls: cannot access '/sys/firmware/efi': No such file or directory

On UEFI systems;

ls -d /sys/firmware/efi

/sys/firmware/efi

You can also simplify your command as follows;

[ -d /sys/firmware/efi ] && echo "UEFI" || echo "BIOS"

Check the Linux Partitioning Scheme

There are two main types of partitioning schemes:

• Master Boot Record (MBR): MBR is the older partitioning scheme and is supported by all BIOS-based computers.
• GUID Partition Table (GPT): GPT is the newer partitioning scheme and is supported by all UEFI-based computers. It is however possible that BIOS based systems use GPT.

Thus, you can simply use commands such as parted or gdisk or fdisk to find out if the system is using BIOS or UEFI.

Using parted command

You can use parted command to determine if the Linux system is using using BIOS or UEFI.

sudo parted /dev/<device> p

Where <device> can be vd{a,b,c...}, or sd{a,b,c...} e.t.c.

For example;

sudo parted /dev/vda p

Sample output for BIOS based system, see Flags section (bios_grub);

Model: Virtio Block Device (virtblk)
Disk /dev/vda: 118GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags: 

Number  Start   End     Size    File system  Name  Flags
 1      1049kB  2097kB  1049kB                     bios_grub
 2      2097kB  1881MB  1879MB  ext4
 3      1881MB  118GB   116GB

Sample output for UEFI based system;

Model: Virtio Block Device (virtblk)
Disk /dev/vda: 107GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags: 

Number  Start   End     Size    File system  Name  Flags
 1      1049kB  1128MB  1127MB  fat32              boot, esp
 2      1128MB  3276MB  2147MB  ext4
 3      3276MB  107GB   104GB

Using gdisk command

You can use gdisk command to determine if Linux system is using BIOS or UEFI as follows;

sudo gdisk -l /dev/<device>

Where <device> can be vd{a,b,c...}, or sd{a,b,c...} e.t.c.

For example;

sudo gdisk -l /dev/vda

Check the Code field for the values, EF00 and EF02.

• If you see the code EF00, it indicates that the partition has the “EFI System Partition” (ESP) attribute set. This is a strong indicator that the partition is used for UEFI booting.
• If you see the code EF02, it represents a BIOS boot partition

Sample output for EFI system;

GPT fdisk (gdisk) version 1.0.8

Partition table scan:
  MBR: protective
  BSD: not present
  APM: not present
  GPT: present

Found valid GPT with protective MBR; using GPT.
Disk /dev/vda: 209715200 sectors, 100.0 GiB
Sector size (logical/physical): 512/512 bytes
Disk identifier (GUID): AF42249F-263F-40FD-93B3-301C8727B9ED
Partition table holds up to 128 entries
Main partition table begins at sector 2 and ends at sector 33
First usable sector is 34, last usable sector is 209715166
Partitions will be aligned on 2048-sector boundaries
Total free space is 4029 sectors (2.0 MiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1            2048         2203647   1.0 GiB     EF00  
   2         2203648         6397951   2.0 GiB     8300  
   3         6397952       209713151   96.9 GiB    8300 

Sample output for BIOS system;

GPT fdisk (gdisk) version 1.0.8

Partition table scan:
  MBR: protective
  BSD: not present
  APM: not present
  GPT: present

Found valid GPT with protective MBR; using GPT.
Disk /dev/vda: 230686720 sectors, 110.0 GiB
Sector size (logical/physical): 512/512 bytes
Disk identifier (GUID): 28658D22-F7C9-45F7-A38A-1A0D7EE63AA2
Partition table holds up to 128 entries
Main partition table begins at sector 2 and ends at sector 33
First usable sector is 34, last usable sector is 230686686
Partitions will be aligned on 2048-sector boundaries
Total free space is 2014 sectors (1007.0 KiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1            2048            4095   1024.0 KiB  EF02  
   2            4096         3674111   1.8 GiB     8300  
   3         3674112       230686686   108.2 GiB   8300 

Using fdisk command

Similarly, you can find out about BIOS or UEFI using fdisk command.

You can use gdisk command to find out if Linux system is using BIOS or UEFI as follows;

sudo fdisk -l /dev/<device>

Where <device> can be vd{a,b,c...}, or sd{a,b,c...} e.t.c.

For example;

sudo fdisk -l /dev/vda

Check the Type column.

BIOS based systems output (Type: BIOS boot);

Disk /dev/vda: 110 GiB, 118111600640 bytes, 230686720 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 28658D22-F7C9-45F7-A38A-1A0D7EE63AA2

Device       Start       End   Sectors   Size Type
/dev/vda1     2048      4095      2048     1M BIOS boot
/dev/vda2     4096   3674111   3670016   1.8G Linux filesystem
/dev/vda3  3674112 230686686 227012575 108.2G Linux filesystem

UEFI based systems output (Type: EFI system);

Disk /dev/vda: 100 GiB, 107374182400 bytes, 209715200 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: AF42249F-263F-40FD-93B3-301C8727B9ED

Device       Start       End   Sectors  Size Type
/dev/vda1     2048   2203647   2201600    1G EFI System
/dev/vda2  2203648   6397951   4194304    2G Linux filesystem
/dev/vda3  6397952 209713151 203315200 96.9G Linux filesystem

Check from System DMI/SMBIOS table using dmidecode

You can check if the Linux system is using BIOS or UEFI from the desktop management interface using dmidecode command.

sudo dmidecode -t 0

Sample output from BIOS;

# dmidecode 3.3
Getting SMBIOS data from sysfs.
SMBIOS 2.8 present.

Handle 0x0000, DMI type 0, 24 bytes
BIOS Information
	Vendor: SeaBIOS
	Version: 1.16.2-debian-1.16.2-1
	Release Date: 04/01/2014
	Address: 0xE8000
	Runtime Size: 96 kB
	ROM Size: 64 kB
	Characteristics:
		BIOS characteristics not supported
		Targeted content distribution is supported
	BIOS Revision: 0.0

Sample output from EFI system;

# dmidecode 3.3
Getting SMBIOS data from sysfs.
SMBIOS 2.8 present.

Handle 0x0000, DMI type 0, 26 bytes
BIOS Information
	Vendor: EFI Development Kit II / OVMF
	Version: 0.0.0
	Release Date: 02/06/2015
	Address: 0xE8000
	Runtime Size: 96 kB
	ROM Size: 64 kB
	Characteristics:
		BIOS characteristics not supported
		Targeted content distribution is supported
		UEFI is supported
		System is a virtual machine
	BIOS Revision: 0.0

Check from kernel startup log using dmesg command

You can also check from the kernel startup logs;

sudo dmesg | grep  "EFI v"

If there is a hit, then the system is UEFI based. If no hit, then it is most likely BIOS.

Sample output;

[    0.000000] efi: EFI v2.70 by EDK II

Check from the Boot Menu

You can also check from the system boot menu. Restart your computer and access the boot menu during the boot process to confirm whether it is using UEFI or BIOS.

And that is it! You have how to check if Linux system is using BIOS or UEFI.

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