# 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

# 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 SE

# To go up one level of the directory tree.  (Change into the parent directory.)cd ..# Go to the $HOME directorycd# Change to the /etc directorycd /etc

# Show free and used space on mounted filesystemsdf -h# Show free and used inodes on mounted filesystemsdf -i# Display disks partitions sizes and typesfdisk -l# Display disk usage for all files and directories in human readable formatdu -ah# Display total disk usage off the current directorydu -sh&n

# Secure copy file.txt to the /tmp folder on serverscp 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 /ho

# Connect to host as your local username.ssh host# Connect to host as userssh user@host# Connect to host using portssh -p port user@host

# Search for pattern in filegrep pattern file# Search recursively for pattern in directorygrep -r pattern directory# Find files and directories by namelocate name# Find files in /home/john that start with "prefix".find /home/john -name 'prefix*'# Find files larger than 100MB in /homefind /home -size

# 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.rpmrpm -i package.rpm# Remove/uninstall package.yum remove package# Install software fr

# 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 

# Display all network interfaces and IP addressip a# Display eth0 address and detailsip addr show dev eth0# Query or control network driver and hardware settingsethtool eth0# Send ICMP echo request to hostping host# Display whois information for domainwhois domain# Display DNS information for domain

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&n

# Display your currently running processesps# Display all the currently running processes on the system.ps -ef# Display process information for processnameps -ef | grep processname# Display and manage the top processestop# Interactive process viewer (top alternative)htop# Kill process with process I

# List all files in a long listing (detailed) formatls -al# Display the present working directorypwd# Create a directorymkdir directory# Remove (delete) filerm file# Remove the directory and its contents recursivelyrm -r directory# Force removal of file without prompting for confirmationrm -f file# 

# 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 "

# Display and manage the top processestop# Interactive process viewer (top alternative)htop# Display processor related statisticsmpstat 1# Display virtual memory statisticsvmstat 1# Display I/O statisticsiostat 1# Display the last 100 syslog messages  (Use /var/log/syslog for Debian based syste

# Display messages in kernel ring bufferdmesg# Display CPU informationcat /proc/cpuinfo# Display memory informationcat /proc/meminfo# Display free and used memory ( -h for human readable, -m for MB, -g for GB.)free -h# Display PCI deviceslspci -tv# Display USB deviceslsusb -tv# Display DMI/SMBIOS (h

# Display Linux system informationuname -a# Display kernel release informationuname -r# Show operating system information such as distribution name and versioncat /etc/os-release# Show how long the system has been running + loaduptime# Show system host namehostname# Display all local IP addresses of