# Module 2.1: Files and navigation

<div id="bkmrk-%3D%3D%3D%3D%3D%3Dreview-so-far%3A">======Review so far:  =================================  
We learned about physical links: </div><div id="bkmrk-ethernet-cables8-wir">

- ethernet cables
- 8 wires in pairs
- on pair is transmit (TX) one is receive (RX)
- full duplex (talking and listening at the same time)

<div>We used terminal to learn about our computer, and to reach out to other computers:</div></div><div id="bkmrk-whoami%2C-last%2C-histor">

- whoami, last, history, top
- ssh (secure shell), ping, traceroute
- nslookup, dig (names to numbers)
- commands and flags (shutdown -r now)
- privileges: root and sudo
- ctrl-c and ctrl-x (stop and halt)

<div>We learned how to scan a network:</div></div><div id="bkmrk-ip-net-monitorarp-sc">

- IP net monitor
- arp-scan
- nmap

<div>We learned about network architecture:</div></div><div id="bkmrk-%C2%A0subnetsip-addresses">

-  subnets
- IP addresses
- 192.168.1.x and 10.14.x.y networks
- gateways
- domain name service (DNS)

<div>We need to learn to navigate around the guts of another computer, locally or remotely: why?</div></div><div id="bkmrk-pwd-tells-you-where-">

- pwd tells you where you are (print working directory) like on a elevator, which floor you are on
- ls tells me what is on that "floor"
- ls -la tells me about even the hidden things on the floor
- ls -lha does all of this in human form
- cd means change directory (floor) on the elevator

<div>Try this:</div></div><div id="bkmrk-sudo-nano-%3Cname%3E-is-">sudo nano &lt;name&gt; is how we create a file</div><div id="bkmrk-in-terminal%2C-navigat">

- in terminal, navigate to your desktop folder
- create a new document called secret: sudo nano secret
- type some secret stuff there
- type ctrl-o (overwrite) and ctrl-x (exit)
- look around your folders for the secret file
- Ok, now repeat the process, creating a file called .hidden (the period makes it hidden)
- type stuff and save
- now look for the file
- ask your friends to find your files by ssh into your machine (don't tell them what you wrote)

</div><div id="bkmrk-to-create-a-new-fold">  
to create a new folder (directory) we use mkdir (make a directory)</div><div id="bkmrk-try-mkdir-mystuff-%28n">

- try mkdir mystuff (no spaces, computers freak out with spaces)
- cd into that folder: cd mystuff
- make a document there
- ask your friends to find it
- look on your desktop for the folder
- create a hidden file there, see if they can find it

<div><div><div>I have hidden a file in another computer, with a reference to yet another computer.</div></div><div>Your challenge is to find the files.</div></div></div>  
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<small>Migrated from Apple Server Wiki. Original page ID: a2L718H</small>