Did you know that there are literally hundreds of Linux commands? Even on a bare-bones Linux server install there are easily over 1,000 different commands.
The interesting thing is that most people only need to use a very small subset of those commands. Below you’ll find a Linux “cheat sheet” that breaks down some of the most commonly used commands by category.
To get your own PDF and printable copy, scroll to the bottom of the page.
Enjoy!
1 – SYSTEM INFORMATION
# Display Linux system information uname -a # Display kernel release information uname -r # Show operating system information such as distribution name and version cat /etc/os-release # Show how long the system has been running + load uptime # Show system host name hostname # Display all local IP addresses of the host. hostname -I # Show system reboot history last reboot # Show the current date and time date # Show this month's calendar cal # Display who is online w # Who you are logged in as whoami
2 – HARDWARE INFORMATION
# Display messages in kernel ring buffer dmesg # Display CPU information cat /proc/cpuinfo # Display memory information cat /proc/meminfo # Display free and used memory ( -h for human readable, -m for MB, -g for GB.) free -h # Display PCI devices lspci -tv # Display USB devices lsusb -tv # Display DMI/SMBIOS (hardware info) from the BIOS dmidecode # Show info about disk sda hdparm -i /dev/sda # Perform a read speed test on disk sda hdparm -tT /dev/sda # Test for unreadable blocks on disk sda badblocks -s /dev/sda
3 – PERFORMANCE MONITORING AND STATISTICS
# Display and manage the top processes top # Interactive process viewer (top alternative) htop # Display processor related statistics mpstat 1 # Display virtual memory statistics vmstat 1 # Display I/O statistics iostat 1 # Display the last 100 syslog messages (Use /var/log/syslog for Debian based systems.) tail -100 /var/log/messages # Capture and display all packets on interface eth0 tcpdump -i eth0 # Monitor all traffic on port 80 ( HTTP ) tcpdump -i eth0 'port 80' # List all open files on the system lsof # List files opened by user lsof -u user # Display free and used memory ( -h for human readable, -m for MB, -g for GB.) free -h # Execute "df -h", showing periodic updates watch df -h
4 – USER INFORMATION AND MANAGEMENT
# Display the user and group ids of your current user. id # Display the last users who have logged onto the system. last # Show who is logged into the system. who # Show who is logged in and what they are doing. w # Create a group named "test". groupadd test # Create an account named john, with a comment of "John Smith" and create the user's home directory. useradd -c "John Smith" -m john # Delete the john account. userdel john # Add the john account to the sales group usermod -aG sales john
5 – FILE AND DIRECTORY COMMANDS
# List all files in a long listing (detailed) format ls -al # Display the present working directory pwd # Create a directory mkdir directory # Remove (delete) file rm file # Remove the directory and its contents recursively rm -r directory # Force removal of file without prompting for confirmation rm -f file # Forcefully remove directory recursively rm -rf directory # Copy file1 to file2 cp file1 file2 # Copy source_directory recursively to destination. If destination exists, copy source_directory into destination, otherwise create destination with the contents of source_directory. cp -r source_directory destination # Rename or move file1 to file2. If file2 is an existing directory, move file1 into directory file2 mv file1 file2 # Create symbolic link to linkname ln -s /path/to/file linkname # Create an empty file or update the access and modification times of file. touch file # View the contents of file cat file # Browse through a text file less file # Display the first 10 lines of file head file # Display the last 10 lines of file tail file # Display the last 10 lines of file and "follow" the file as it grows. tail -f file
6 – PROCESS MANAGEMENT
# Display your currently running processes ps # Display all the currently running processes on the system. ps -ef # Display process information for processname ps -ef | grep processname # Display and manage the top processes top # Interactive process viewer (top alternative) htop # Kill process with process ID of pid kill pid # Kill all processes named processname killall processname # Start program in the background program & # Display stopped or background jobs bg # Brings the most recent background job to foreground fg # Brings job n to the foreground fg n
7 – FILE PERMISSIONS
PERMISSION EXAMPLE U G W rwx rwx rwx chmod 777 filename rwx rwx r-x chmod 775 filename rwx r-x r-x chmod 755 filename rw- rw- r-- chmod 664 filename rw- r-- r-- chmod 644 filename # NOTE: Use 777 sparingly! LEGEND U = User G = Group W = World r = Read w = write x = execute - = no access
8 – NETWORKING
# Display all network interfaces and IP address ip a # Display eth0 address and details ip addr show dev eth0 # Query or control network driver and hardware settings ethtool eth0 # Send ICMP echo request to host ping host # Display whois information for domain whois domain # Display DNS information for domain dig domain # Reverse lookup of IP_ADDRESS dig -x IP_ADDRESS # Display DNS IP address for domain host domain # Display the network address of the host name. hostname -i # Display all local IP addresses of the host. hostname -I # Download http://domain.com/file wget http://domain.com/file # Display listening tcp and udp ports and corresponding programs netstat -nutlp
9 – ARCHIVES (TAR FILES)
# Create tar named archive.tar containing directory. tar cf archive.tar directory # Extract the contents from archive.tar. tar xf archive.tar # Create a gzip compressed tar file name archive.tar.gz. tar czf archive.tar.gz directory # Extract a gzip compressed tar file. tar xzf archive.tar.gz # Create a tar file with bzip2 compression tar cjf archive.tar.bz2 directory # Extract a bzip2 compressed tar file. tar xjf archive.tar.bz2
10 – INSTALLING PACKAGES
# Search for a package by keyword. yum search keyword # Install package. yum install package # Display description and summary information about package. yum info package # Install package from local file named package.rpm rpm -i package.rpm # Remove/uninstall package. yum remove package # Install software from source code. tar zxvf sourcecode.tar.gz cd sourcecode ./configure make make install
11 – SEARCH
# Search for pattern in file grep pattern file # Search recursively for pattern in directory grep -r pattern directory # Find files and directories by name locate name # Find files in /home/john that start with "prefix". find /home/john -name 'prefix*' # Find files larger than 100MB in /home find /home -size +100M
12 – SSH LOGINS
# Connect to host as your local username. ssh host # Connect to host as user ssh user@host # Connect to host using port ssh -p port user@host
13 – FILE TRANSFERS
# Secure copy file.txt to the /tmp folder on server scp file.txt server:/tmp # Copy *.html files from server to the local /tmp folder. scp server:/var/www/*.html /tmp # Copy all files and directories recursively from server to the current system's /tmp folder. scp -r server:/var/www /tmp # Synchronize /home to /backups/home rsync -a /home /backups/ # Synchronize files/directories between the local and remote system with compression enabled rsync -avz /home server:/backups/
14 – DISK USAGE
# Show free and used space on mounted filesystems df -h # Show free and used inodes on mounted filesystems df -i # Display disks partitions sizes and types fdisk -l # Display disk usage for all files and directories in human readable format du -ah # Display total disk usage off the current directory du -sh
15 – DIRECTORY NAVIGATION
# To go up one level of the directory tree. (Change into the parent directory.) cd .. # Go to the $HOME directory cd # Change to the /etc directory cd /etc
16 – SECURITY
# Change the current user's password. passwd # Switch to the root account with root's environment. (Login shell.) sudo -i # Execute your current shell as root. (Non-login shell.) sudo -s # List sudo privileges for the current user. sudo -l # Edit the sudoers configuration file. visudo # Display the current SELinux mode. getenforce # Display SELinux details such as the current SELinux mode, the configured mode, and the loaded policy. sestatus # Change the current SELinux mode to Permissive. (Does not survive a reboot.) setenforce 0 # Change the current SELinux mode to Enforcing. (Does not survive a reboot.) setenforce 1 # Set the SELinux mode to enforcing on boot by using this setting in the /etc/selinux/config file. SELINUX=enforcing # Set the SELinux mode to permissive on boot by using this setting in the /etc/selinux/config file. SELINUX=permissive # Set the SELinux mode to disabled on boot by using this setting in the /etc/selinux/config file. SELINUX=disabled
17 – LOGGING AND AUDITING
# Display messages in kernel ring buffer. dmesg # Display logs stored in the systemd journal. journalctl # Display logs for a specific unit (service). journalctl -u servicename