How can I tell if my system was booted as EFI/UEFI or BIOS?

Question

How do I determine whether a particular running Ubuntu system was booted using EFI/UEFI, or BIOS?

Answer 1

The easiest way is to check to see if /sys/firmware/efi exists. It does not appear if you booted using traditional BIOS.

#!/bin/bash
[ -d /sys/firmware/efi ] && echo UEFI || echo BIOS

Answer 2

Deprecated

The answer below is a method that may not always work.
Instead use Colin's answer based on /sys/firmware/efi.

---

It's very easy to tell if a system was booted in EFI (or not, in which case it must be BIOS):

Just use dmesg | grep "EFI v"

• This will return a line like this, if the system was booted off of EFI:

  [ 0.000000] EFI v2.00 by American Megatrends

• Or return nothing if it was not, in which case it was booted off of BIOS

Example of bash script usage based on grep's exit code:

...
dmesg | grep -q "EFI v"    # -q tell grep to output nothing
if [ $? -eq 0 ]      # check exit code; if 0 EFI, else BIOS
then
    echo "You are using EFI boot."
  else
    echo "You are using BIOS boot"
fi
...

Source: For how to determine if an EFI system is using legacy-BIOS emulation or not, as well as more information on testing for EFI and EFI compatibility, along with the strings for a number of EFI vendors/versions, please see this page from the Ubuntu Developer Summit for Precise.

Answer 3

"Disk" (or gnome-disks) is quite handy I've found in that when you boot into your OS, and bring up "Disk", look at the EFI partition and if it shows mounted then you're in UEFI. But if the EFI partition show not mounted then your in BIOS

Answer 4

Python code to check if system is booted with UEFI or ROM BIOS:

import os,sys
def main():
    if(os.path.exists("/sys/firmware/efi")):
        print"\n\n System is booted with uefi!"
    else:
        print"\n\n System is booted with rom bios"
main()
sys.exit(0)