Linux command line basics

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Linux Command Line Interface, (CLI from now on) could be at first glance discouraging for the average Joe, since nowadays we are only used to Graphic Interfaces. But don’t let you down, using a command line shell could be, not only very useful, but also kind of funny. This guide will help you move your first steps in the command shell environment.

First, when a Command Line Interface could be useful for you?

  • Remote Connection via SSH: SSH remote connection allows to interact with UDOO without physical access to it. SSH is available only with command line interface.
  • Using a minimal Linux Distribution without a graphical interface. Some Linux Distribution come without a Graphical User Interface, in order to maximize available resources. Command line interface is your only bet in this scenario Some power-users consider CLI the most convenient way to perform code execution and file-system operations. Even if you are not in this category, you may found out that CLI can be very fast when you get used to it.

To help you get started, here are some very basic Linux commands:

sudo

Your first ally, allows users to run programs with the security privileges of root, or superuser.Its name is a concatenation of “su” (substitute user) and “do”, or take action . So, if you get an error message saying that “only root can do that”, just use the same command with preceeded by sudo.

sudo su

This just enables root privileges once for all, without forcing you to type sudo everytime. It works until you close the shell you are working into.

sudo su touch

create an empty file

nano

open an handy text editor, to save and exit, press “ctrl” and “x”, and tell yes or no by pressing “y” or “n”

cat

cat shows the content of a file, it speeds up file inspection for smaller files. eg: cat /etc/hostname

ls

Shows you the content of a folder

cd

opens a specific folder

cd..

Brings you to a higher folder level

cd /

brings you to root (top filesystem level)

rm

deletes a file

rm -rf

deletes a folder

mv

moves a file or a folder. Useful for renaming also eg mv myfile /myfolder/myfile mv myfile mysecondfile

cp

copies a file e.g. cp myfile /home/ubuntu/

cp -R

copies a folder e.g. cp -R myfolder /home/ubuntu/myfolder

mkdir

creates a folder

top

Top is a very useful utility, it basically gives you a complete overview of the system’s status. It produces an ordered list of running processes selected by user-specified criteria. Top shows how much processing power and memory are being used, as well as other information about the running processes.

df -h

Shows used and available disk space, in megabytes.

ifconfig -a

Shows networking useful data, like current ip, netmasks and other statistics.

chmod

chmod let you set files permissions. This utility is very important for people concerned about security, but it is useful also for coders, since you can set a script as executable with it .

dmesg

Shows the messages resulting from the most recent system boot. It is useful for troubleshooting, since you can see which modules are loaded, which binaries are started and so on.

sync

Thanks to this command your SD card lifespan will drastically improve, remember to launch it every time you turn Udoo off, or remove the power. Completes all pending input/output operations. It must be launched as root, or with sudo.

reboot

reboots the system

shutdown

shuts it down