kexec is a fast reboot feature (and system call) that lets you reboot to a new Linux kernel, without having to go through the BIOS/firmware hardware initialisation or the bootloader.
Systems with high availability requirements (trading system, medical, critical databases) and kernel developers who have to continually reboot their systems benefit most from using kexec.
Because kexec skips the most time-consuming parts of system reboot, namely the BIOS/firmware stage, reboots are extremely quick and availability is significantly increased.
You must have enabled the option CONFIG_KEXEC compiled into your kernel to use this feature.
# Setup kexec kexec -l --append="`cat /proc/cmdline`" --initrd=/boot/initramfs-`uname -r`.img /boot/vmlinuz-`uname -r` # Reboot kernel sync; umount -a ; kexec -e