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Getting started with tcpdump
At some point you want to know what packets are flowing on your network. Use tcpdump for this. The man page is obtuse, to say the least, so here are some simple commands to get you started. -n means show IP numbers and don't try to translate them to names. -l means write a line as soon as it is ready. -i eth0 means trace the packets flowing through the first ethernet interface. src or dst w.x.y.z traces only packets going to or from IP address w.x.y.z. port 80 traces only packets for HTTP. proto udp traces only packets for UDP protocol. Once you are happy with each option combine them with 'and' 'or' 'not' to get the effects you want.

Install pip with Proxy
Installs pip packages defining a proxy

Convert images (jpg, png, ...) into a PDF
Converts images (maybe from scans) into a PDF

Creates a symbolic link or overwrites an existing one
-n: dereference the existing link -v: (optional) to be sure of what is being done -f: force the deletion of the existing one -s: creates a symlink Be careful: the destination can also be a file or a directory and it will be overwritten.

To get internet connection information .
To get the connection information of protocol tcp and extended infortmation.

pop-up messages on a remote computer
Run this command when you are physically at the computer you wish to send pop-up messages to. Then when you ssh in to it, you can do this: echo "guess who?" > commander guess who? will then pop up on the screen for a few moments, then disappear. You will need to create the commander file first. I mess with my wife all the time with this. i.e. echo "You have given the computer a virus. Computer will be rendered useless in 10 seconds." > commander lol

Killing processes with your mouse in an infinite loop
Useful for quickly cleaning your Desktop. Nice joke if launched at startup.

Copy sparse files
This causes cp to detect and omit large blocks of nulls. Sparse files are useful for implying a lot of disk space without actually having to write it all out. http://en.wikipedia.org/wiki/Sparse_file You can use it in a pipe too: $ dd if=/dev/zero bs=1M count=5 |cp --sparse=always /dev/stdin SPARSE_FILE

Fork Bomb for Windows
Quick and dirty forkbomb for all flavors of windows Do not use in production. Replace start with a command of your choice, this will just open a new command prompt and is pretty tricky to stop once started

Which processes are listening on a specific port (e.g. port 80)
swap out "80" for your port of interest. Can use port number or named ports e.g. "http"


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