If you are planning to use a hard disk of size more than 2TB UEFI comes into the picture. Today, I came across a situation where I had to turn off transparent huge pages on one of the RHEL 7 servers. To make change, I had to modify default grub file i.e /etc/default/grub and reconfigure grub configuration file. Now the based-on boot option the grub configuration file changes as below.
BIOS-based Machines: /boot/grub2/grub.cfg
UEFI-based Machines: /boot/efi/EFI/redhat/grub.cfg
Now, I was not sure if the server is BIOS booted or UEFI. Below are the ways to check if server is booted with BIOS/UEFI
1. Check if directory “/sys/firmware/efi” exist on the server. If not means, server is BIOS booted.
$ sudo ls -l /sys/firmware/efi ls: cannot access /sys/firmware/efi: No such file or directory
2. Check executing below command. If command is not working, make sure package “efibootmgr” is installed on the server.
$ sudo efibootmgr EFI variables are not supported on this system.
As the command is not showing any EFI variables, the server is BIOS booted.