Xterm

==This page requires major clean-up!

The basics
user@computer:~$ echo "hello world"

hello world


 * says/outputs/prints text to sdtout

user@computer:~$ echo $USER

user


 * says/outputs/prints the currently logged in user's name

user@computer:~$ echo $PWD

/home/user


 * says/outputs/prints the current CD'ed directory

user@computer:~$ cd /home/user/MyDocs


 * Change Directory to another one. Can also be relative location, in this case $ cd MyDocs

user@computer:~/MyDocs$ echo $PWD /home/user/MyDocs

user@computer:~/MyDocs$ cd ~
 * Change Directory to home directory. Can also be relative location, in this case $ cd ..

user@computer:~$ mkdir asdf


 * Create a directory/folder

user@computer:~$ rm -R /home/user/asdf
 * Be very careful with the remove command. Especially with the -R recursive parameter which deletes any files and folders within a specified folder

user@computer:~$ uname -r

2.6.21-omap1


 * List the kernel version. the -a parameter outputs all known information

user@computer:~$ ls -A /home/user/MyDocs

.documents .......... .sounds

.games .................. .videos

.images ................. randomfile


 * Lists all files and directories, including hidden ones. Hidden files and directories start with a dot/period

user@computer:~$ cat /etc/resolv.conf

#nameserver 127.0.0.1

nameserver 192.168.1.1

#nameserver 4.2.2.2


 * Cat spits out an entire text file to terminal. resolv.conf (remember *NIX is case-sensitive) is where DNS servers are stored. The # pound character comments/"comments out" aka disables a line of text in a BASH script/file

user@computer:~$ ps | awk '{ print $5 }'

...

/usr/bin/osso-xterm

/usr/libexec/gnome-vfs-daemon

bash

ps

awk


 * ps lists running processes, you might also be interested in the interactive top command. piped to awk which in this case says to only show the 5th column (separated by tab characters)

user@computer:~$ foobar='example'; echo $foobar

example


 * Basic example of a variable

user@computer:~$ uname -s > /dev/shm/os; cat /dev/shm/os


 * Example of directing output to a file. Files stored in /dev/shm are stored directly in RAM and thus are deleted on shutdown

Writing a shell function
user@computer:~$ minute { foo=`date +%S`; echo $foo; if [ "$foo" -lt "30" ]; then echo "under half"; else echo "over half"; fi; }


 * Simple shell function that uses a variable and if/then/else logic

user@computer:~$ minute

29

under half


 * Using the shell function we just wrote, outputs the current time in seconds (only the seconds part) and whether it is closer to the last minute or next minute. Shell functions are only available for the terminal session. Save in .bashrc or .profile to be persistent/saved

user@computer:~$ minute

31

over half '''

Intermediate
user@computer:~$ /usr/bin/camera &


 * Everything is run from a terminal, quite literally in *NIX. A GUI program is a running instance of a terminal process. Therefore the camera program can be launched. The & amperstand tells it to disassociate from the current terminal and create it's own process

user@computer:~$ ln -s /sbin/ifconfig /usr/bin


 * The user PATH does not include /sbin for some reason by default on NITs, which is annoying as typing in /sbin/ifconfig - which should be in /usr/bin/ anyway. Thus we are going to symlink it.

user@computer:~$''' ifconfig | grep "inet addr"


 * Example use of grep. grep outputs the entire line matching the pattern, in this case "inet addr" which is piped into it from the output of ifconfig using the | pipe character

user@computer:~$ ifconfig | grep "inet addr" | awk '{ print $2 }' | cut -d : -f2


 * Advanced example pipes from ifconfig to grep to awk and finally to cut to output the clean IP address which can then be fed into something else if desired

==Logged in as root from here on out. Not necessary for every command but for some of them. If you have sudoer installed you can simply prefix each command with sudo. If not you are gonna use an equivalent of sudo su - or simply login a root using another method. For easyroot users, simply type $ root and enter.==

This next section is Debian-based specific
root@computer:~# apt-cache search nano

nano-tiny - free Pico clone

traceroute-nanog - Determine route of packets

nano - nano editor


 * Searches repos for packages by keyword

root@computer:~# apt-get install nano

install package nano. It's an easy to use CLI text editor.

root@computer:~# wget http://nitstuff.appspot.com/dists/chinook/user/binary-armel/nano_2.0.6_armel.deb


 * Instead of using the repos using wget to download .deb package from website.

root@computer:~# dpkg -i nano_2.0.6_armel.deb


 * Installing locally saved debian package.

The following is networking specific
root@computer:~# ssh name@192.168.1.100

...

Are you sure you want to continue connecting (yes/no)?yes

name@desktop:~$ exit


 * SSH example. Specify the user _at_ the IP address of the computer you want to access. Keep in mind that this works only over LAN by default (you need to forward port 22 on the router and give outside IP address or use some type of fake VPN). If you get a RSA error message, simply delete ~/.ssh/known_hosts using $ rm ~/.ssh/known_hosts Type exit to leave remote session

root@computer:~# scp name@192.168.1.100:/home/name/randomfile /home/user/

user@computer:~$ ls /home/user/randomfile


 * File is copied from remote computer to local computer to user's home directory. Root's home directory is /root

root@computer:~# ssh name@192.168.1.100

name@desktop:~$ screen

name@desktop:~$ hello


 * Leaves a shared session open

friend@laptop:~$ ssh name@192.168.1.100

name@desktop:~$ hello world


 * Allows you to work with a friend or simply resume a session later. Good for long tasks that need to disconnect from a machine and reconnect later.

root@computer:~# ssh name@192.168.1.100

name@desktop:~$ screen -ln nano /etc/resolv.conf


 * [Nano instance]

[CTRL]+[A]+[D]


 * Detaches from a screen leaving a process running on a remote machine

name@desktop:~$ exit

root@computer:~# ssh name@192.168.1.100

name@desktop:~$ screen -r


 * [Nano instance]

[CTRL]+[X]

name@desktop:~$ exit


 * [screen is terminating]

name@desktop:~$ exit

root@computer:~#


 * Detach a process. If you are running a process via ssh on a remote machine, the process is killed when the connection is interrupted, unless it was detached with screen.