dd if=/dev/zero of=/tmp/zero.img bs=10M count=100000
watch -n 5 pkill -USR1 ^dd$
watch -n 5 killall -USR1 dd
while killall -USR1 dd; do sleep 5; done
while (ps auxww |grep " dd " |grep -v grep |awk '{print $2}' |while read pid; do kill -USR1 $pid; done) ; do sleep 5; done