killall crond
killall f
killall i

delete:

/bin/i
/bin/f  ... fail


yum -y install e2fsprogs  (need chattr)


cd /bin
lsattr  (look for ----i-------- /bin/f )
chattr -i f
rm /bin/f   (now it works)


chattr -i /etc/crontab    (that was ----i--------)