[Raspberry pi] Make raspberry as a wifi router

According to ref 1 and ref 2, raspberry pi can be a DHCP server and assign IP by wifi interface.
Now must set some settings, let make raspberry pi can be a wifi route which the flow can pass by eth0.
Set

Way 1
sudo echo 1 > /proc/sys/net/ipv4/ip_forward

Way 2
sudo vim /etc/sysctl.conf
# Uncomment the next line to enable packet forwarding for IPv4
net.ipv4.ip_forward=1
#Start command at the reboot

crontab -e
@reboot /home/pi/start.sh

create a file was called start.sh which under /home/pi

sudo iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
sleep 5
sudo /etc/init.d/isc-dhcp-server restart
sleep 5
sudo /etc/init.d/isc-dhcp-server restart
sleep 5
sudo /etc/init.d/isc-dhcp-server restart
Why 「sudo /etc/init.d/isc-dhcp-server restart」do three time, because I must make sure the server start up after reboot.
After above procedure, then raspberry pi be a wifi router now.

Reference:
1.  [Raspberry Pi] Install DHCP Server into Raspberry Pi
2. [Raspberry Pi] WiFi-AP by using Edimax(EW-7811UN)
3. Raspberry Pi as a Router
4. Run script on a startup