=========
CLI Tools
=========
-------------------------------
netcat, tar, rsync, iperf, tee
-------------------------------


.. class:: right

    Morgan Goose

    April 2011

.. class:: handout

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Netcat
=======

    "Netcat is a featured networking utility which reads and writes data
    across network connections, using the TCP/IP protocol.
    It is designed to be a reliable "back-end" tool that can be used
    directly or easily driven by other programs and scripts. At the same
    time, it is a feature-rich network debugging and exploration tool,
    since it can create almost any kind of connection you would need and
    has several interesting built-in capabilities." - netcat_

.. _netcat: http://netcat.sourceforge.net/

Simple use
==========

Think of it as a network pipe akin to | and here it is sending a file across
the network.

.. code-block:: bash

    #Server1
    $ cat some.tgz | nc 80

    #Server2
    $ nc Server1 80 > some.tgz


Proxy
======

This starts a nc server on port 12345 and all the connections get redirected to
google.com:80, as well as sending te response back to the web browser.

.. code-block:: bash

    $ nc -l 12345 -c 'nc www.google.com 80'


tar
===

In computing, tar (derived from tape archive and commonly referred to as
"tarball") is both a file format (in the form of a type of archive bitstream)
and the name of a program used to handle such files. - wikipedia_

.. _wikipedia: http://en.wikipedia.org/wiki/Tar_%28file_format%29

.. raw:: html

    <div style="background: white">
      <img src="./400px-Targzip.svg.png" />
    </div>


This is a tar pipe
===================

Since tar takes pushes to stdout and can recieve stdin

.. code:: bash

    (cd src && tar -cf - .) | (cd dest && tar -xpf -)

We can say change to src dir, and tar it up through a pipe to untar it in a
dest dir. Or put simply "copy the src directory to dst, preserving permissions
and other special stuff." - `extra cheese`_

.. _extra cheese: http://blog.extracheese.org/2010/05/the-tar-pipe.html


Why that's cool
================

We can go back to *netcat* and use it to send data over a network (ssh can be
used as well, but I mentioned nc)

.. code:: bash

    #Server2 (receiving)
    $ netcat -l -p 7000 | tar x

    #Server1 (sending)
    $ tar cf - * | netcat Server2 7000

*note* I used the **-l** flag here to explicitly have a server listen for
incoming, instead of pulling from the implicit serve of like the first example


Side note on pipes and netcat
=============================

You can also use this method to image/clone disk with remotely

.. code:: bash

    #Server2 (receiving)
    $ nc -l -p 7000 | dd of=/dev/hda

    #Server1 (sending)
    $ dd if=/dev/hda | nc Server2 7000 -q 10


To be even more leet
=====================

Pipe it through gzip to compress it before transfer

.. code:: bash

    #Server2 (receiving)
    $ nc -l -p 7000 | gzip -dfc | dd of=/dev/had

    #Server1 (sending)
    $ dd if=/dev/hda | gzip -cf | nc Server2 7000 -q 10


rsync
=====

.. code::

    coolest flag: --link-dest=DIR

Unchanged files are hard linked from DIR to the destination directory. The
files must be identical in all preserved attributes in order for the files to 
be linked together.

Beginning in version 2.6.4, multiple --link-dest directories may be provided,
which will cause rsync to search the list in the order specified for an exact
match.

This  option  works  best  when copying into an empty destination hierarchy, as
rsync treats existing files as definitive.


iperf
=====

A commonly used network testing tool that can create TCP and UDP data streams
and measure the throughput of a network that is carrying them.

.. raw:: html

    <div style="background: white">
      <img src="./iperf_labo.gif" />
    </div>


Looks like this
===============

.. code:: 
    Client side:
    
    #iperf -c 10.1.1.1
    ------------------------------------------------------------
    Client connecting to 10.1.1.1, TCP port 5001
    TCP window size: 16384 Byte (default)
    ------------------------------------------------------------
    [ 3] local 10.6.2.5 port 33453 connected with 10.1.1.1 port 5001
    [ 3]   0.0-10.2 sec   1.26 MBytes   1.05 Mbits/sec

    Server side:
    
    #iperf -s
    ------------------------------------------------------------
    Server listening on TCP port 5001
    TCP window size: 8.00 KByte (default)
    ------------------------------------------------------------
    [852] local 10.1.1.1 port 5001 connected with 10.6.2.5 port 33453
    [ ID]   Interval          Transfer       Bandwidth
    [852]   0.0-10.6 sec   1.26 MBytes   1.03 Mbits/sec 


tee
===

normally used to split the output of a program so that it can be seen on the
display and also be saved in a file.

.. raw:: html

    <div style="background: white">
      <img src="./400px-Tee.svg.png" />
    </div>

Good for logging only stdout, but seeing both stdout and stderr in the
terminal, while making a sort of logfile of the program run.