Common Linux Commands

# Add a user
# Basic usage: useradd [options] username
sudo useradd -s /bin/bash -m -c "Fname Lname" -Gwheel <username>

# Set a password for new user:
sudo passwd <username>

# Set to prompt user to change password at login:
sudo passwd --expire <username>

# Add a User to Multiple Groups
sudo groupadd admins
sudo groupadd webadmin
sudo groupadd developers
sudo usermod -a -G admins,webadmin,developers <username>
sudo useradd -G admins,webadmin,developers <username>

# Add user to a group
# groupadd - add current user to a group
sudo groupadd <newgroup>
# usermod - add specified user to a group
usermod -a -G <examplegroup> <username>

# File and Directory managment
ls         # List directory contents
ls -a      # Do not ignore entries starting with .
ls -h      # List file sizes in human-readable format
ls -l      # Use long listing format
ls -lha    # May combine switches
pwd        # Print working directory
cd         # Change current directory
mkdir      # Create a new directory
rm         # Remove files or directories
rm -rf     # Remove directory and all contents/subfolders
cp         # Copy files and folders
mv         # Move files and folders

# File Content Managment
cat        # Concatenate and display file contents
less       # View file contents one page at a time
head       # View the first part of files
tail       # View the last part of files

# User and Permissions Managment
sudo       # Execute a command as a superuser
passwd     # Change user password
chmod      # Change the permissions of files and folders

# Process Managment
ps         # Report a shapshot of the corrent processes
kill       # Kill a process - need PID (process ID)

# System Information
uname     # Display system information, -a for all information
df        # Display file system disk space usage
free      # Display amount of free and used memory in the system

# Network Managment
ping      # Test network connectivity
ifconfig  # Configure network interface parameters
hostname -I # Show IP address
ip addr   # Display IP address of NICs

# Software updater
systemctl stop packagekit
systemctl disable packagekit