Essential Linux commands

This guide covers the most frequently used Linux commands to help you navigate, manage, and troubleshoot your server with confidence and speed.

System information

uname -r                  # Show Linux kernel version
uname -a                  # Detailed system information
arch                      # Display processor architecture
cat /proc/cpuinfo         # View CPU specifications
cat /proc/meminfo         # Detailed memory statistics
cat /proc/swaps           # Show swap partition information
free -h                   # Display memory usage (human-readable)
df -h                     # Show disk space usage
lsblk                     # List all block devices (disks and partitions)
dmidecode -q              # Get hardware component info from BIOS
lspci -tv                 # List PCI devices in a tree view
lsusb -tv                 # List USB devices in a tree view
date                      # Display current date and time

Power management

reboot                    # Restart the system immediately
shutdown -h now           # Power off the server immediately
shutdown -r now           # Reboot the server immediately
shutdown -h 22:00         # Schedule a shutdown at 22:00
shutdown -c               # Cancel a scheduled shutdown

File and directory operations

pwd                       # Print the current working directory
ls                        # List files in the current directory
ls -la                    # Show all files, including hidden ones (.dotfiles)
ls -lh                    # List files with human-readable sizes
cd /path/to/dir           # Change to a specific directory
cd ..                     # Move up one directory level
cd ~                      # Jump to the user's home directory
cd -                      # Switch back to the previous directory

mkdir folder              # Create a new directory
mkdir -p /path/to/folder  # Create nested directories (parent folders included)

cp file1 file2            # Copy a file
cp -r dir1 dir2           # Copy a directory and its contents recursively

mv file1 file2            # Rename or move a file/directory
rm file                   # Delete a file
rm -rf folder             # Force-delete a folder and all its contents (use with caution!)

ln -s file link           # Create a symbolic link

Search and filtering

find / -name filename     # Search for a file by name starting from root
find /var/www -name "*.php" # Find all .php files in a specific directory

grep "text" file          # Search for a specific string within a file
grep -r "text" /path      # Recursively search for a string across all files in a path

locate filename           # Fast search via database (update it using 'updatedb')
whereis command           # Locate binary, source, and manual page for a command
which command             # Identify the path of the executable being run

Storage and file systems

df -h                     # Check disk usage across all mounted systems
du -sh /path              # Display total size of a specific directory
lsblk                     # Overview of disks and partitions
mount                     # List all currently mounted file systems
umount /dev/sda1          # Unmount a specific partition

Users and permissions

whoami                    # Identify the current logged-in user
id                        # Show UID, GID, and groups for the current user
cat /etc/passwd           # View the list of all system users
cat /etc/group            # View the list of all system groups

useradd username          # Create a new system user
passwd username           # Set or change a user's password
userdel -r username       # Delete a user and their home directory

groupadd groupname        # Create a new user group
usermod -aG group username # Add an existing user to a group

Networking

ip addr                   # Display network interfaces and IP addresses
ip route                  # Show the system routing table
ping host                 # Check connectivity to a host
curl -I domain.com        # Fetch HTTP headers from a website
wget url                  # Download a file from the internet
netstat -tuln             # List active connections and listening ports
ss -tuln                  # Modern, faster alternative to netstat

Pro tips

• RTFM: use man command or command --help to access documentation for any utility.
• Paging: for long outputs, pipe the result to | less or | more to scroll comfortably.
• Piping: combine multiple commands using the pipe operator (|) to filter and process data on the fly.