With UEFI becoming the de-facto firmware for system initialization and BIOS mode being kept only for compatibility, Linux doesn't seem to have a straightforward way of determining the mode the OS is booted by. Here's a quick solution -- if UEFI, there exists a directory "/sys/firmware/efi". Otherwise, the booting mode would be legacy-BIOS.
"systemd", the most comprehensive and feature-rich init system has been a new wave in the way Linux' userspace is managed. Among the many new tools the suite provides, systemd-analyze is the one that gives primary information about the system's boot performance. To see the time spent in kernel space and user space during booting, run … Continue reading “systemd-analyze” — Blame Ain’t Nobody For Boot Wait