File and Directory Operations
ls – Lists the contents of a directory.
ls
ls -l # Long listing format
ls -a # List all files, including hidden ones
cd – Changes the current directory.
cd /path/to/directory
cd .. # Go up one directory
cd ~ # Go to the home directory
mkdir – Creates a new directory.
mkdir new_directory
rmdir – Removes an empty directory.
rmdir directory_name
cp – Copies files or directories.
cp source_file destination
cp -r source_directory destination_directory # Copy directories recursively
mv – Moves or renames files and directories.
mv old_name new_name
mv file_name /path/to/destination/
rm – Removes files or directories.
rm file_name
rm -r directory_name # Remove directories recursively
touch – Creates an empty file or updates the timestamp of an existing file.
touch file_name
File Viewing & Manipulation
cat – Displays the contents of a file.
cat file_name
less – Allows you to view file contents page by page.
less file_name
head – Shows the first 10 lines of a file (default).
head file_name
head -n 5 file_name # Show the first 5 lines
tail – Shows the last 10 lines of a file (default).
tail file_name
tail -n 5 file_name # Show the last 5 lines
grep – Searches for patterns within files.
grep ‘search_term’ file_name
grep -r ‘search_term’ /path/to/directory # Search recursively in directories
Permissions & Ownership
chmod – Changes file permissions.
chmod 755 file_name # Gives read, write, execute permissions to the owner and read, execute to others
chmod +x script.sh # Make file executable
chown – Changes the file owner and group.
chown user:group file_name
umask – Sets default file creation permissions.
umask 022 # Sets default permissions to 755 for directories and 644 for files
Process Management
ps – Displays the currently running processes.
ps
ps aux # Show all processes
top – Displays real-time system processes and resource usage.
top
kill – Terminates a process by its PID.
kill process_id
kill -9 process_id # Forcefully kill a process
htop – Interactive process viewer (requires installation).
htop
System Information
df – Shows disk space usage.
df -h # Human-readable format
du – Shows disk usage for files and directories.
du -h /path/to/directory
free – Displays memory usage.
free -h # Human-readable format
uname – Shows system information.
uname -a # Display all system info
uptime – Shows how long the system has been running.
uptime
whoami – Displays the current logged-in user.
whoami
hostname – Displays or sets the system’s hostname.
hostname
lscpu – Displays CPU architecture information.
lscpu
Network Commands
ping – Tests connectivity to a host.
ping google.com
ifconfig – Displays network interface information (may require net-tools installation on some systems).
ifconfig
ip – Configures network interfaces and routing.
ip addr show # Show IP addresses of network interfaces
ip route show # Show routing table
curl – Fetches data from a URL.
curl https://example.com
wget – Downloads files from the web.
wget https://example.com/file.zip
Package Management
apt-get (for Debian/Ubuntu-based distributions) – Installs, updates, or removes software packages.
sudo apt-get update # Update package list
sudo apt-get install package # Install a package
sudo apt-get remove package # Remove a package
yum (for RedHat/CentOS-based distributions) – Installs, updates, or removes software packages.
sudo yum update # Update package list
sudo yum install package # Install a package
sudo yum remove package # Remove a package
File Compression
tar – Archives or extracts files.
tar -czvf archive_name.tar.gz /path/to/directory # Create a compressed archive
tar -xzvf archive_name.tar.gz # Extract a compressed archive
zip – Compresses files into a zip archive.
zip archive_name.zip file1 file2
unzip – Extracts a zip archive.
unzip archive_name.zip
Miscellaneous
echo – Prints a message or variables to the terminal.
echo “Hello, World!”
date – Displays or sets the system date and time.
date
alias – Creates an alias for a command.
alias ll=’ls -la’ # Create a shortcut for ‘ls -la’
history – Shows the command history.
history
clear – Clears the terminal screen.
clear
These are just a few of the many powerful commands in Linux, but they cover most of the common operations you’ll perform daily.