Is your firewall blocking connection from a host and still you want to unblock the IP address of the remote host? Here is one way of doing it:

1. Do a listing of firewall rules and grep the IP (eg. 1.2.3.4)
$ /sbin/iptables -L INPUT -n –line-numbers | grep 1.2.3.4

-write down the line number.
-If the chain name is different or user defined, replace “INPUT” by the relevant chain name such as OUTPUT.

2. Delete the line number (eg. for line number 99 and chain INPUT)

$/sbin/iptables -D INPUT 99

@credit to: http://www.cyberciti.biz/faq/iptables-delete-ip-address-subnet-from-linux-firewall/

It seems that the controversy surrounding the Google and Verizon proposal on managing Internet traffic has re-ignited the debate on Net Neutrality. The proposal claims to be in favor of open Internet, but with some exceptions like wireless services! It makes you wonder, isn’t wireless the future of the Internet? “GoRizon” have also suggested some on line services to be excluded from Net Neutrality principles, like health care monitoring, “advanced educational services, or new entertainment and gaming options.” With so much uncertainty as to which form of Internet traffic regulation would benefit society at large, it might help to brain storm on certain scenarios which could happen if we go ahead with one or other form of regulation.Sarah Kessler has compiled 7 such scenarios“Net Neutrality: 7 Worst Case Scenarios”.

Normally if you want to block all requests to and from an IP address, iptables is an ideal solution. A rule similar to this one would be handy

/sbin/iptables -A INPUT -s 1.2.3.4 -j DROP

What if you want to block that IP without using iptables, route command would do the job

/sbin/route add -host 1.2.3.4 reject

-List files opened by a program listening on a certain port (lsof -i:port)

lsof -i:3306

-Benchmark the performance of a webserver

ab -n 100 -c 5 http://www.sample-mysite.com/test.php

Send 100 request with 5 concurrent connections.

-Search for a string/pattern in all subdirectories of the given path

 find /my/path -exec grep 'hairy' {} /dev/null \;

While watching this video, your job is to count how many times the players in white shirt pass the ball.