Linux_logo_errorbits.comHere is a list that contains one of the most used Linux commands, and a short explanation for them:
– list – lists files and directories, can be used with a lot of options like: -a, -R, -l, -g, -r;

pwd – print working directory – shows the path of the current directory;

ifconfig – interface configuration – used to view and change the configuration of the network;

cd – change directory – used to change the current working directory;

df – disk free – must be used with -h option(the values will be displayed in KB/MB/GB);

du – disk usage – must be used with -h option, -s option will sum the subfolders and files capacity;

grep – global regular expression print – processes text line by line and returns the value that matches the request;

cat / tac – catenate – is the simplest way to display the contents of a file, directly in command line interface / tac reverses the order of the contents;

tail – outputs the last part of the contents of a file;

tee – used to dublicate input and to route it to multiple outputs at once;

touch – used to update the access and modification time of a file, if the file does not exist it is created with the specified name;

mkdir – make directory – used to create directories;

rm – remove – used to remove/delete files or directories;

cp – copy – used to make copies of files and directories;

less – is a simple command line file viewer;

head –  used to display the first part of files;

file – used to determine the file’s type;

wc – word count – counts the words in a file / -m counts characters / -l counts lines;

ln – link – creates links between files;

find – searches the file system for the specified file;

locate / slocate – it searches in a database, it’s faster than “find” but not that accurate;

yum – used to install/remove packages, update/upgrade system (CentOS);

apt or apt-get – used to install/remove packages, update/upgrade system (Ubuntu);

whoami – shows the current user username;

who – shows the list of usernames;

uname – displays the operating system type, -a switch can be used for more details like distribution/version/kernel/release;

less /proc/cpuinfo – shows CPU hardware information;

cat /proc/meminfo – displays used and free memory information;

[updating with new commands…]

Useful links:

Linux Directory Map / Structure

Introduction to Linux

Using Help in Linux

Download and install Oracle VirtualBox

How to install CentOS on Oracle VirtualBox