Why is the CRON script not running on boot?

Question

linux

Good afternoon. The script does not work in the cron at the start of the computer
Cron edited from the root
Line from the cron. Only the command echo
@reboot /root/firewall.sh > /root/firewall.log gets into the log file

Here is the script

#!/bin/bash
#sleep 60
sleep 30
echo 'Firewall script'
systemctl disable ufw;
systemctl stop ufw;
iptables -A INPUT -i lo -j ACCEPT;
iptables -A INPUT -p icmp --icmp-type  0 -j ACCEPT;
iptables -A INPUT -p icmp --icmp-type  3 -j ACCEPT;
iptables -A INPUT -p icmp --icmp-type  4 -j ACCEPT;
iptables -A INPUT -p icmp --icmp-type 11 -j ACCEPT;
iptables -A INPUT -p icmp --icmp-type 12 -j ACCEPT;
iptables -A INPUT -p tcp  -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT;
iptables -A INPUT -s 188.242.*.* -p tcp --dport 22 -j ACCEPT;
iptables -A INPUT -p tcp --dport 10000 -j ACCEPT;
iptables -A INPUT -i tun+ -j ACCEPT;
iptables -A INPUT -i tap+ -j ACCEPT;
iptables -A INPUT -j DROP;
iptables -A OUTPUT -j ACCEPT;

Answer 1

Cron by default does not know the path to directories with programs.
Specify full paths to systemctl and iptables.

Answer 2

Add to the beginning of the script set -xand it will hit not onlyecho