Thankfully pinging from an Ubuntu server is very similar to how its done on Windows systems.

To ping a website or ip address 4 times use

ping -c 4 hostname

to do 8 requests

ping -c 8 hostname

Without the -c parameter the ping requests will keep running until you manually cancel it. The -c stands for count and stops the ping after that amount of packets have been sent.

You can read more up on ping at the Ubuntu manual.