Determine the boot mode of the operating system - Amazon Elastic Compute Cloud
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Determine the boot mode of the operating system

The boot mode of the AMI guides Amazon EC2 on which boot mode to use to boot an instance. To view whether the operating system of your instance is configured for UEFI, you need to connect to your instance using SSH.

To determine the boot mode of the instance’s operating system

  1. Connect to your Linux instance using SSH.

  2. To view the boot mode of the operating system, try one of the following:

    • Run the following command.

      [ec2-user ~]$ sudo /usr/sbin/efibootmgr

      Expected output from an instance booted in UEFI boot mode

      BootCurrent: 0001
Timeout: 0 seconds
BootOrder: 0000,0001
Boot0000* UiApp
Boot0001* UEFI Amazon Elastic Block Store vol-xyz

    • Run the following command to verify the existence of the /sys/firmware/efi directory. This directory exists only if the instance boots using UEFI. If this directory doesn't exist, the command returns Legacy BIOS Boot Detected.

      [ec2-user ~]$ [ -d /sys/firmware/efi ] && echo "UEFI Boot Detected" || echo "Legacy BIOS Boot Detected"

      Expected output from an instance booted in UEFI boot mode

      UEFI Boot Detected

      Expected output from an instance booted in Legacy BIOS boot mode

      Legacy BIOS Boot Detected

    • Run the following command to verify that EFI appears in the dmesg output.

      [ec2-user ~]$ dmesg | grep -i "EFI"

      Expected output from an instance booted in UEFI boot mode

      [    0.000000] efi: Getting EFI parameters from FDT:
[    0.000000] efi: EFI v2.70 by EDK II