/etc/init.d/kexec is in kexec-tools 1:2.0.7-5.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 | #! /bin/sh
### BEGIN INIT INFO
# Provides:		kexec
# Required-Start:
# Required-Stop:   	reboot
# X-Stop-After:		umountroot
# Default-Start:	2 3 4 5
# Default-Stop:		6
# Short-Description: Execute the kexec -e command to reboot system
# Description:
### END INIT INFO
PATH=/sbin:/bin
. /lib/lsb/init-functions
test -r /etc/default/kexec && . /etc/default/kexec
do_stop () {
	test "x`cat /sys/kernel/kexec_loaded`y" = "x1y" || exit 0
	test -x /sbin/kexec || exit 0
	log_action_msg "Will now restart with kexec"
	# Clear the screen if possible
	printf "\033[;H\033[2J"
        /sbin/kexec -e
        log_failure_msg "kexec failed"
}
case "$1" in
  start)
	# No-op
	;;
  restart|reload|force-reload)
	echo "Error: argument '$1' not supported" >&2
	exit 3
	;;
  stop)
	do_stop
	;;
  *)
	echo "Usage: $0 start|stop" >&2
	exit 3
	;;
esac
exit 0
 |