man <tool> | 
Opens man pages for the specified tool. | 
<tool> -h | 
Prints the help page of the tool. | 
apropos <keyword> | 
Searches through man pages’ descriptions for instances of a given keyword. | 
cat | 
Concatenate and print files. | 
whoami | 
Displays current username. | 
id | 
Returns users identity. | 
hostname | 
Sets or prints the name of the current host system. | 
uname | 
Prints operating system name. | 
pwd | 
Returns working directory name. | 
ifconfig | 
The ifconfig utility is used to assign or view an address to a network interface and/or configure network interface parameters. | 
ip | 
Ip is a utility to show or manipulate routing, network devices, interfaces, and tunnels. | 
netstat | 
Shows network status. | 
ss | 
Another utility to investigate sockets. | 
ps | 
Shows process status. | 
who | 
Displays who is logged in. | 
env | 
Prints environment or sets and executes a command. | 
lsblk | 
Lists block devices. | 
lsusb | 
Lists USB devices. | 
lsof | 
Lists opened files. | 
lspci | 
Lists PCI devices. | 
sudo | 
Execute command as a different user. | 
su | 
The su utility requests appropriate user credentials via PAM and switches to that user ID (the default user is the superuser).  A shell is then executed. | 
useradd | 
Creates a new user or update default new user information. | 
userdel | 
Deletes a user account and related files. | 
usermod | 
Modifies a user account. | 
addgroup | 
Adds a group to the system. | 
delgroup | 
Removes a group from the system. | 
passwd | 
Changes user password. | 
dpkg | 
Install, remove and configure Debian-based packages. | 
apt | 
High-level package management command-line utility. | 
aptitude | 
Alternative to apt. | 
snap | 
Install, remove and configure snap packages. | 
gem | 
Standard package manager for Ruby. | 
pip | 
Standard package manager for Python. | 
git | 
Revision control system command-line utility. | 
systemctl | 
Command-line based service and systemd control manager. | 
ps | 
Prints a snapshot of the current processes. | 
journalctl | 
Query the systemd journal. | 
kill | 
Sends a signal to a process. | 
bg | 
Puts a process into background. | 
jobs | 
Lists all processes that are running in the background. | 
fg | 
Puts a process into the foreground. | 
curl | 
Command-line utility to transfer data from or to a server. | 
wget | 
An alternative to curl that downloads files from FTP or HTTP(s) server. | 
python3 -m http.server | 
Starts a Python3 web server on TCP port 8000. | 
ls | 
Lists directory contents. | 
cd | 
Changes the directory. | 
clear | 
Clears the terminal. | 
touch | 
Creates an empty file. | 
mkdir | 
Creates a directory. | 
tree | 
Lists the contents of a directory recursively. | 
mv | 
Move or rename files or directories. | 
cp | 
Copy files or directories. | 
nano | 
Terminal based text editor. | 
which | 
Returns the path to a file or link. | 
find | 
Searches for files in a directory hierarchy. | 
updatedb | 
Updates the locale database for existing contents on the system. | 
locate | 
Uses the locale database to find contents on the system. | 
more | 
Pager that is used to read STDOUT or files. | 
less | 
An alternative to more with more features. | 
head | 
Prints the first ten lines of STDOUT or a file. | 
tail | 
Prints the last ten lines of STDOUT or a file. | 
sort | 
Sorts the contents of STDOUT or a file. | 
grep | 
Searches for specific results that contain given patterns. | 
cut | 
Removes sections from each line of files. | 
tr | 
Replaces certain characters. | 
column | 
Command-line based utility that formats its input into multiple columns. | 
awk | 
Pattern scanning and processing language. | 
sed | 
A stream editor for filtering and transforming text. | 
wc | 
Prints newline, word, and byte counts for a given input. | 
chmod | 
Changes permission of a file or directory. | 
chown | 
Changes the owner and group of a file or directory. |