SYS: Use /proc/sys and sysctl to modify and set kernel runtime parameters.

Edit the /etc/sysctl.conf file and add the following lines:

net.ipv4.ip_forward = 1                  # allow IPv4 forwarding
net.ipv4.icmp_echo_ignore_all = 1        # don't respond to a ping
net.ipv4.icmp_echo_ignore_broadcasts = 1 # don't respond to a ping to the broadcast address

Put the changes into practice:

# sysctl -p

Check the changes:

# cat /proc/sys/net/ipv4/ip_forward
# cat /proc/sys/net/ipv4/icmp_echo_ignore_all
# cat /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts