Linux Commands Cheat Sheet: A Quick Reference Guide
32 min read
Mastering Linux starts with knowing the right commands. This Linux Commands Cheat Sheet is your go-to guide, offering quick access to essential commands that can simplify your tasks. From file management to system checks, this cheat sheet ensures you’re always equipped to get things done efficiently. Whether you’re just starting or looking to boost your command line skills, these key commands will streamline your workflow and save you time.
1. File and Directory Management
# File and Directory Management
ls [-a] [-l] [-h] [-t] [-r] [-R] [directory]
# List directory contents
# -a : show hidden files
# -l : long listing format
# -h : human-readable sizes
# -t : sort by modification time
# -r : reverse order
# -R : list subdirectories recursively
# Example:
ls -lh /home/user
cd [directory]
# Change directory
# Example:
cd /var/www/html
pwd
# Print working directory
# Example:
pwd
cp [-r] [-i] [-u] [-v] source destination
# Copy files and directories
# -r : copy directories recursively
# -i : prompt before overwrite
# -u : copy only when source is newer than destination
# -v : verbose output
# Example:
cp -r /source/directory /destination/directory
mv [-i] [-n] [-v] source destination
# Move or rename files and directories
# -i : prompt before overwrite
# -n : do not overwrite an existing file
# -v : verbose output
# Example:
mv -i oldfile.txt newfile.txt
rm [-r] [-f] [-i] [-v] file
# Remove files or directories
# -r : remove directories and contents recursively
# -f : force remove without confirmation
# -i : prompt before every removal
# -v : verbose output
# Example:
rm -rf /unwanted/directory
mkdir [-p] [-v] directory
# Make directories
# -p : create parent directories if needed
# -v : verbose output
# Example:
mkdir -p /new/parent/directory
rmdir [-p] directory
# Remove empty directories
# -p : remove parent directories if empty
# Example:
rmdir -p /empty/parent/directory
touch [-c] [-d time] [-t timestamp] filename
# Change file timestamps or create empty files
# -c : do not create file if it does not exist
# -d time : set modification time
# -t timestamp : use a specific timestamp
# Example:
touch -t 202401011230 file.txt
find [directory] [-name "filename"] [-type f/d] [-size +100M] [-mtime -7] [-exec command {} \;]
# Search for files in a directory hierarchy
# -name "filename" : search by filename
# -type f/d : search for files (f) or directories (d)
# -size +100M : find files larger than 100MB
# -mtime -7 : find files modified in the last 7 days
# -exec command {} \; : execute a command on found files
# Example:
find /home -type f -name "*.log" -size +50M
locate [-i] filename
# Find files by name (uses a prebuilt database)
# -i : case-insensitive search
# Example:
locate -i config.php
tree [-L level] [-d] [-f] [directory]
# Display directories in a tree-like format
# -L : limit depth of directory tree
# -d : show directories only
# -f : show full file path
# Example:
tree -L 2 -d /var/www
chmod [-R] mode file
# Change file permissions
# -R : apply changes recursively
# Example:
chmod -R 755 /var/www/html
chown [-R] owner:group file
# Change file owner and group
# -R : apply changes recursively
# Example:
chown -R user:group /var/www/html
chgrp [-R] group file
# Change group ownership
# -R : apply changes recursively
# Example:
chgrp -R developers /var/www/html
stat [-c format] file
# Display file or file system status
# -c : specify custom output format
# Example:
stat -c "%U %G %s %y" file.txt 2. File Viewing and Editing
# File Viewing and Editing
cat [options] filename
# Concatenate and display file content
# -n : number all output lines
# -E : display `$` at the end of each line
# Example:
cat -n file.txt
tac [options] filename
# Concatenate and display file content in reverse
# Example:
tac file.txt
more [options] filename
# View file content interactively (page by page)
# -num : specify number of lines per page
# Example:
more -20 file.txt
less [options] filename
# View file content interactively (scrollable)
# -N : show line numbers
# Example:
less -N file.txt
head [options] filename
# Output the first part of a file
# -n num : display the first ‘num’ lines
# Example:
head -n 10 file.txt
tail [options] filename
# Output the last part of a file
# -n num : display the last ‘num’ lines
# -f : continuously monitor a file for updates
# Example:
tail -f /var/log/syslog
nano filename
# Open nano text editor (terminal-based)
# Example:
nano file.txt
vim filename
# Open Vim text editor
# Example:
vim file.txt
vi filename
# Open Vi text editor
# Example:
vi file.txt
emacs filename
# Open Emacs text editor
# Example:
emacs file.txt
grep [options] "pattern" filename
# Search text using patterns
# -i : case-insensitive search
# -v : invert match (exclude lines matching pattern)
# -r : search recursively in directories
# Example:
grep -i "error" /var/log/syslog
sed [options] 'script' filename
# Stream editor for filtering and transforming text
# -i : edit files in place
# -e : add a script to execute
# Example:
sed -i 's/oldword/newword/g' file.txt
awk ['pattern {action}'] filename
# Pattern scanning and processing language
# Example:
awk '{print $1, $3}' file.txt
cut [options] filename
# Remove sections from each line of files
# -d : specify a delimiter
# -f : specify field numbers
# Example:
cut -d':' -f1 /etc/passwd
sort [options] filename
# Sort lines of text files
# -r : reverse the sorting order
# -n : numeric sort
# Example:
sort -n file.txt
uniq [options] filename
# Report or omit repeated lines
# -c : prefix lines with the number of occurrences
# Example:
uniq -c file.txt 3. Process Management
# Process Management
ps [options]
# Report a snapshot of current processes
# -e : show all processes
# -f : full-format listing
# -u user : show processes for a specific user
# Example:
ps -ef
top [options]
# Display Linux tasks dynamically
# -u user : show processes for a specific user
# -n num : update display ‘num’ times before exiting
# Example:
top -u root
htop
# Interactive process viewer (advanced top)
# Example:
htop
kill [options] PID
# Send a signal to a process, typically to terminate
# -9 : force kill a process
# -15 : terminate a process gracefully
# Example:
kill -9 1234
killall [options] process_name
# Terminate processes by name
# -9 : force kill all processes with the given name
# Example:
killall -9 firefox
bg [job_id]
# Resume a suspended job in the background
# Example:
bg %1
fg [job_id]
# Bring a job to the foreground
# Example:
fg %1
jobs
# List active jobs
# Example:
jobs
nice [-n adjustment] command
# Run a program with modified scheduling priority
# Default priority is 0, lower values give higher priority
# Example:
nice -n 10 myscript.sh
renice priority -p PID
# Alter priority of running processes
# Example:
renice 5 -p 1234
uptime
# Show how long the system has been running
# Example:
uptime
time command
# Measure program running time
# Example:
time ls -l 4. Disk Management
# Disk Management
df [options]
# Report file system disk space usage
# -h : human-readable format
# -T : show file system type
# -i : display inode usage
# Example:
df -h
du [options] [directory]
# Estimate file space usage
# -h : human-readable format
# -s : show total size of a directory
# -c : display grand total
# Example:
du -sh /var/log
fdisk [options] device
# Partition table manipulator for Linux
# -l : list partition tables
# Example:
fdisk -l
lsblk [options]
# List information about block devices
# -f : show file system type
# -o : specify columns to display
# Example:
lsblk -f
mount [options] device mount_point
# Mount a file system
# -t type : specify file system type
# -o options : mount with specific options
# Example:
mount -t ext4 /dev/sdb1 /mnt
umount [options] device/mount_point
# Unmount a file system
# -l : lazy unmount
# -f : force unmount
# Example:
umount /mnt
parted [options] device
# A partition manipulation program
# -l : list partition details
# Example:
parted -l
mkfs [options] -t type device
# Create a file system
# -t type : specify file system type (ext4, xfs, etc.)
# Example:
mkfs -t ext4 /dev/sdb1
fsck [options] device
# File system consistency check and repair
# -y : automatically repair issues
# -n : check only, do not repair
# Example:
fsck -y /dev/sdb1
blkid [options]
# Locate/print block device attributes
# Example:
blkid /dev/sdb1 5. Networking
# Networking
ifconfig [interface] [options]
# Configure network interfaces (deprecated, use 'ip' instead)
# -a : display all interfaces
# up : enable interface
# down : disable interface
# Example:
ifconfig eth0 up
ip [options] object [command]
# Show/manipulate routing, devices, and tunnels
# addr : show IP addresses
# route : show routing table
# link : show network interfaces
# Example:
ip addr show
ping [options] host
# Send ICMP Echo requests to network hosts
# -c count : send a specific number of packets
# -i interval : set interval between packets
# Example:
ping -c 5 google.com
netstat [options]
# Display network statistics (deprecated, use 'ss' instead)
# -t : show TCP connections
# -u : show UDP connections
# -a : show all connections
# Example:
netstat -tulnp
ss [options]
# Show socket statistics (faster alternative to netstat)
# -t : show TCP connections
# -u : show UDP connections
# -l : show listening ports
# Example:
ss -tulnp
traceroute [options] host
# Trace the route packets take to a network host
# -n : show numeric addresses only
# -m max_hops : set max number of hops
# Example:
traceroute -n google.com
nslookup [options] domain
# Query Internet name servers interactively
# Example:
nslookup example.com
dig [options] domain
# DNS lookup utility
# +short : show concise output
# Example:
dig google.com
wget [options] URL
# Non-interactive network downloader
# -O filename : specify output file
# -q : quiet mode
# Example:
wget -O file.html https://example.com
curl [options] URL
# Transfer data with URLs
# -o filename : specify output file
# -I : fetch headers only
# Example:
curl -o file.html https://example.com
scp [options] source destination
# Secure copy files between hosts
# -r : copy directories recursively
# Example:
scp file.txt user@192.168.1.10:/home/user/
ssh [options] user@host
# Secure shell for remote login
# -p port : specify port
# Example:
ssh -p 22 user@192.168.1.10
ftp [options] host
# File Transfer Protocol client
# Example:
ftp ftp.example.com 6. User and Group Management
# User and Group Management
useradd [options] username
# Add a user to the system
# -m : create the user's home directory
# -s shell : specify default shell
# Example:
useradd -m -s /bin/bash john
usermod [options] username
# Modify a user account
# -aG group : add user to a group
# -s shell : change the user's shell
# Example:
usermod -aG sudo john
userdel [options] username
# Delete a user account
# -r : remove the user's home directory and mail spool
# Example:
userdel -r john
groupadd [options] groupname
# Add a group to the system
# -g gid : specify group ID
# Example:
groupadd developers
groupdel groupname
# Delete a group
# Example:
groupdel developers
passwd [options] username
# Change user password
# -e : expire the user's password immediately
# Example:
passwd john
chage [options] username
# Change user password expiry information
# -l : list password expiration info
# -M max_days : set max days between password changes
# Example:
chage -M 30 john
whoami
# Print the current logged-in user
# Example:
whoami
who [options]
# Show who is logged in
# -u : show idle time
# Example:
who -u
w [options]
# Show who is logged in and what they’re doing
# -h : suppress header
# Example:
w -h
id [options] username
# Display user and group information
# -u : display user ID
# -g : display group ID
# -G : display all groups the user belongs to
# Example:
id john
groups [username]
# Show user’s groups
# Example:
groups john 7. System Information and Monitoring
# System Information and Monitoring
uname [options]
# Print system information
# -a : show all system information
# -r : show the kernel release
# Example:
uname -a
hostname [options]
# Show or set the system’s hostname
# -i : show the system's IP address
# -f : show the fully qualified domain name
# Example:
hostname -i
uptime
# How long the system has been running
# Example:
uptime
dmesg [options]
# Boot and system messages
# -T : show human-readable timestamps
# -n level : set the level of messages to display
# Example:
dmesg -T
free [options]
# Display memory usage
# -h : human-readable format
# -m : display in megabytes
# Example:
free -h
top [options]
# Display Linux tasks dynamically
# -u user : show processes for a specific user
# -n num : update display ‘num’ times before exiting
# Example:
top -u root
vmstat [options]
# Report virtual memory statistics
# -s : display summary statistics
# -a : show active memory
# Example:
vmstat -s
lscpu
# Display information about the CPU architecture
# Example:
lscpu
lsusb
# List USB devices
# Example:
lsusb
lspci
# List PCI devices
# Example:
lspci
lshw [options]
# List hardware configuration
# -short : display in a shorter format
# -html : generate HTML output
# Example:
lshw -short 8. Archiving and Compression
# Archiving and Compression
tar [options] [archive] [file(s)]
# Archive files
# -c : create an archive
# -x : extract an archive
# -f : specify the archive file
# -z : compress with gzip
# -j : compress with bzip2
# -J : compress with xz
# Example:
tar -czf archive.tar.gz /path/to/directory # Compress files using gzip
tar -xzf archive.tar.gz # Extract gzipped tarball
tar -cf archive.tar /path/to/directory # Create a tarball
tar -xf archive.tar # Extract tarball
zip [options] archive.zip [file(s)]
# Package and compress files into a ZIP archive
# -r : recursively zip directories
# -9 : set the compression level (1-9, where 9 is the highest)
# Example:
zip -r archive.zip /path/to/directory
unzip [options] archive.zip
# Extract files from a ZIP archive
# -d directory : extract to a specific directory
# Example:
unzip archive.zip -d /path/to/extract
gzip [options] file
# Compress files using the gzip algorithm
# -d : decompress the file
# -k : keep the original file after compression
# Example:
gzip file.txt # Compress file
gzip -d file.txt.gz # Decompress file
gunzip [options] file.gz
# Decompress files compressed with gzip
# Example:
gunzip file.txt.gz
bzip2 [options] file
# Compress files using the bzip2 algorithm
# -d : decompress the file
# -k : keep the original file after compression
# Example:
bzip2 file.txt # Compress file
bzip2 -d file.txt.bz2 # Decompress file
bunzip2 [options] file.bz2
# Decompress files compressed with bzip2
# Example:
bunzip2 file.txt.bz2
xz [options] file
# Compress files using the xz algorithm
# -d : decompress the file
# -k : keep the original file after compression
# Example:
xz file.txt # Compress file
xz -d file.txt.xz # Decompress file
unxz [options] file.xz
# Decompress files compressed with xz
# Example:
unxz file.txt.xz 9. Package Management (Depends on Distribution)
# Package Management (Depends on Distribution)
# Debian-based (e.g., Ubuntu)
apt-get [options] command
# APT package handling utility
# install : install a package
# update : update package list
# upgrade : upgrade installed packages
# remove : remove a package
# Example:
apt-get install vim # Install a package
apt-get update # Update package list
apt-get upgrade # Upgrade installed packages
apt-get remove vim # Remove a package
apt-cache [options] command
# Query APT cache
# search : search for a package
# show : show package details
# Example:
apt-cache search vim # Search for a package
apt-cache show vim # Show package details
# Red Hat-based (e.g., CentOS, Fedora)
yum [options] command
# Package manager for RPM-based systems
# install : install a package
# update : update installed packages
# remove : remove a package
# Example:
yum install vim # Install a package
yum update # Update installed packages
yum remove vim # Remove a package
dnf [options] command
# Next-generation package manager (Fedora, CentOS 8+)
# install : install a package
# update : update installed packages
# remove : remove a package
# Example:
dnf install vim # Install a package
dnf update # Update installed packages
dnf remove vim # Remove a package 10. General Commands
# General Commands
rpm [options] <package>
# RPM package manager
# -i : install an RPM package
# -e : remove an RPM package
# Example:
rpm -i package.rpm # Install an RPM package
rpm -e package # Remove an RPM package
dpkg [options] <package>
# Debian package manager
# -i : install a Debian package
# -r : remove a Debian package
# Example:
dpkg -i package.deb # Install a Debian package
dpkg -r package # Remove a Debian package 11. System Services and Daemon Management
# System Services and Daemon Management
systemctl [options] <service>
# Control the systemd system and service manager
# start : start a service
# stop : stop a service
# restart : restart a service
# enable : enable a service to start on boot
# disable : disable a service from starting on boot
# status : check service status
# Example:
systemctl start apache2 # Start a service
systemctl stop apache2 # Stop a service
systemctl restart apache2 # Restart a service
systemctl enable apache2 # Enable a service to start on boot
systemctl disable apache2 # Disable a service from starting on boot
systemctl status apache2 # Check service status
service [options] <service>
# Older service management command (used in non-systemd systems)
# start : start a service
# stop : stop a service
# restart : restart a service
# status : check service status
# Example:
service apache2 start # Start a service
service apache2 stop # Stop a service
service apache2 restart # Restart a service
service apache2 status # Check service status 12. Scheduling Tasks
# Scheduling Tasks
cron
# Daemon for running scheduled commands
# Example:
# Edit, list, or remove cron jobs using the crontab command (listed below).
crontab [options]
# Manage cron jobs for the current user
# -e : edit cron jobs
# -l : list the current user’s cron jobs
# -r : remove the current user's cron jobs
# Example:
crontab -e # Edit cron jobs for the current user
crontab -l # List the current user’s cron jobs
crontab -r # Remove the current user's cron jobs
at [time]
# Run commands at a specified time
# Example:
at 09:00 # Schedule a command to run at 09:00 AM
batch
# Run commands when the system load is low
# Example:
batch # Run commands when the system load is low
sleep [time]
# Delay for a specified time
# Example:
sleep 5s # Sleep for 5 seconds 13. File Permissions and Security
# File Permissions and Security
chmod [options] <file>
# Change file permissions
# -r : recursively change permissions for directories and their contents
# Example:
chmod 755 file.txt # Change file permissions to rwx-r-xr-x
chmod -r 755 /path/to/directory # Change permissions recursively
chown [options] <user>:<group> <file>
# Change file owner and group
# -R : recursively change ownership for directories and their contents
# Example:
chown user:group file.txt # Change file owner and group
chown -R user:group /path/to/directory # Change ownership recursively
chgrp [options] <group> <file>
# Change the group ownership of a file
# -R : recursively change group ownership for directories and their contents
# Example:
chgrp group file.txt # Change group ownership of a file
chgrp -R group /path/to/directory # Change group ownership recursively
umask [mode]
# Set default permissions for new files
# Example:
umask 022 # Set default permissions for new files
setfacl [options] <file>
# Set file access control lists (ACL)
# -m : modify ACL
# -x : remove an ACL
# Example:
setfacl -m u:username:rw file.txt # Set ACL to allow a user read/write access
getfacl [options] <file>
# Get file access control lists (ACL)
# Example:
getfacl file.txt # Get the ACL of a file
sudo [command]
# Execute a command as another user (usually root)
# Example:
sudo apt-get update # Execute command as root
visudo
# Edit the sudoers file safely
# Example:
visudo # Edit the sudoers file safely
passwd [options] <user>
# Change a user’s password
# Example:
passwd # Change the password of the current user
passwd username # Change the password for a specific user
sudoers
# Manage sudo access for users
# Example:
# This is typically edited using visudo (listed above).
gpasswd [options] <group>
# Administer group password
# Example:
gpasswd groupname # Administer password for a group
ss [options]
# Display socket statistics (for secure network connections)
# -t : show TCP sockets
# -u : show UDP sockets
# Example:
ss -tuln # Show listening sockets for TCP and UDP 14. System Backup and Restore
# System Backup and Restore
rsync [options] <source> <destination>
# Remote file and directory synchronization
# -a : archive mode (preserve symbolic links, permissions, timestamps, etc.)
# -v : verbose
# -z : compress file data during transfer
# Example:
rsync -avz source/ destination/ # Synchronize files
rsync -avz -e ssh source/ user@remote:/destination/ # Sync over SSH
cpio [options]
# Copy files to and from archives
# Example:
# cpio is typically used in conjunction with other commands like find for backup and restore
find /path/to/files | cpio -ov > backup.cpio # Create a backup archive
cpio -iv < backup.cpio # Extract files from the archive
dd [options]
# Low-level copying and backup of entire filesystems
# if : input file or device
# of : output file or device
# Example:
dd if=/dev/sda of=/path/to/backup.img # Backup a disk/partition
dd if=/path/to/backup.img of=/dev/sda # Restore a disk/partition 15. System Diagnostics and Troubleshooting
# System Diagnostics and Troubleshooting
dmesg [options]
# Print the kernel ring buffer messages (system boot and hardware-related messages)
# Example:
dmesg # View kernel ring buffer messages
journalctl [options]
# Query and view logs from systemd’s journal
# Example:
journalctl # View all systemd logs
journalctl -u apache2 # View logs for a specific service
strace [options] <command>
# Trace system calls and signals
# Example:
strace ls # Trace the system calls of the ls command
lsof [options]
# List open files (useful for debugging)
# Example:
lsof # List all open files
lsof /path/to/file # Show processes using a specific file
vmstat [options]
# Report virtual memory statistics
# Example:
vmstat 1 # Report every second
iostat [options]
# Report CPU and I/O statistics
# Example:
iostat # Report CPU and I/O statistics
mpstat [options]
# Report CPU usage statistics
# Example:
mpstat 1 # Report CPU usage every second
pidstat [options]
# Report statistics by process
# Example:
pidstat 1 # Report process statistics every second
free [options]
# Display memory usage
# Example:
free -h # Display memory usage in human-readable format
uptime
# How long the system has been running
# Example:
uptime # Show system uptime
watch [options] <command>
# Execute a program periodically, showing output
# -n : interval in seconds
# Example:
watch -n 1 free # Watch memory usage every second
lshw [options]
# List hardware configuration
# Example:
lshw # List detailed hardware configuration
htop
# Interactive process viewer (better than top)
# Example:
htop # Launch the interactive process viewer
netstat [options]
# Network statistics (deprecated in favor of ss)
# Example:
netstat # Show network statistics
ss [options]
# Show socket statistics (more efficient than netstat)
# Example:
ss -tuln # Show listening TCP/UDP sockets 16. Networking & Remote Management
# Networking & Remote Management
ifconfig [options]
# Configure network interfaces (older command, replaced by ip)
# Example:
ifconfig # View or configure network interfaces
ip [options]
# A more modern alternative for managing network interfaces and routing
# ip addr : Show IP addresses
# ip link : Show or manipulate network interfaces
# ip route : Show or manipulate routing tables
# Example:
ip addr # Show IP addresses
ip link # Show or manipulate network interfaces
ip route # Show or manipulate routing tables
ss [options]
# Display socket statistics (useful for diagnosing network issues)
# Example:
ss -tuln # Show listening TCP/UDP sockets
nmap [options]
# Network exploration tool (can be used for security auditing)
# Example:
nmap -sP 192.168.1.0/24 # Scan a network range
telnet [options]
# User interface to the TELNET protocol (less common nowadays)
# Example:
telnet <host> # Connect to a remote host via TELNET
nc (Netcat) [options]
# Network utility for reading and writing from network connections
# -l : listen mode
# -p : port
# Example:
nc -l -p 1234 # Listen on port 1234
nc <host> <port> # Connect to a host and port
iptables [options]
# Administration tool for IPv4 packet filtering and NAT (Network Address Translation)
# Example:
iptables -L # List current iptables rules
firewalld [options]
# Frontend for managing firewall rules (used in some distros like Fedora and CentOS)
# Example:
firewalld --zone=public --add-port=80/tcp # Allow HTTP traffic
ufw [options]
# Uncomplicated firewall (front-end for iptables)
# -enable : enable firewall
# -allow <port> : allow traffic on a specific port
# Example:
ufw enable # Enable firewall
ufw allow 80 # Allow HTTP traffic
tcpdump [options]
# Command-line packet analyzer
# Example:
tcpdump -i eth0 # Capture packets on interface eth0
curl [options]
# Transfer data from or to a server using various protocols (HTTP, FTP, etc.)
# Example:
curl -O http://example.com/file.txt # Download a file
wget [options]
# Download files from the web via HTTP, HTTPS, FTP
# Example:
wget http://example.com/file.txt # Download a file
scp [options]
# Secure copy over SSH (used to copy files between systems)
# Example:
scp file.txt user@remote:/path/to/destination/ # Copy file to remote server
rsync [options]
# Remote file and directory synchronization (often used for backups)
# Example:
rsync -avz /local/path/ remote:/remote/path/ # Sync directories 17. Text Processing Utilities
# Text Processing Utilities
grep [options] 'pattern' [file]
# Search for patterns within files
# -r : recursively search in directories
# Example:
grep 'pattern' file.txt # Search for a pattern in a file
grep -r 'pattern' /dir/ # Recursively search for a pattern
sed [options]
# Stream editor for filtering and transforming text
# s/old/new/g : replace 'old' with 'new' globally
# Example:
sed 's/old/new/g' file.txt # Replace old with new globally
awk [options]
# A powerful text processing language
# {print $1} : print the first column of each line in a file
# Example:
awk '{print $1}' file.txt # Print the first column of each line in a file
cut [options]
# Remove sections from each line of a file
# -d : delimiter
# -f : field(s) to extract
# Example:
cut -d ':' -f 1 /etc/passwd # Print the first field of each line, delimited by ":"
sort [options]
# Sort lines of text files
# Example:
sort file.txt # Sort file content in ascending order
uniq [options]
# Report or omit repeated lines in a file
# Example:
sort file.txt | uniq # Sort and remove duplicate lines
tee [options]
# Read from standard input and write to standard output and files
# Example:
echo "text" | tee file.txt # Write to file and show output on screen
tr [options]
# Translate or delete characters
# Example:
echo "hello" | tr 'a-z' 'A-Z' # Convert lowercase to uppercase
paste [options]
# Merge lines of files
# Example:
paste file1.txt file2.txt # Combine lines of file1 and file2 side by side
wc [options]
# Word, line, character, and byte count
# -l : count lines
# -w : count words
# Example:
wc -l file.txt # Count lines in a file
wc -w file.txt # Count words in a file 18. System Shutdown and Reboot
# System Shutdown and Reboot
shutdown [options]
# Shut down the system
# -h : halt the system
# -r : reboot the system
# +<time> : shut down after specified minutes
# Example:
shutdown -h now # Immediately shut down
shutdown -r now # Reboot the system
shutdown -h +10 # Shut down after 10 minutes
reboot
# Reboot the system
# Example:
reboot # Reboot the system
halt
# Halt the system immediately (equivalent to turning off power)
# Example:
halt # Stop all system processes
poweroff
# Power off the system
# Example:
poweroff # Turn off the system
init [runlevel]
# Change the runlevel (old-style system manager)
# 0 : shutdown
# 6 : reboot
# Example:
init 0 # Shutdown
init 6 # Reboot19. File System Mounting and Management
# File System Mounting and Management
mount [options] [device] [mount-point]
# Mount a file system
# Example:
mount /dev/sda1 /mnt # Mount partition to a directory
umount [options] [mount-point]
# Unmount a file system
# Example:
umount /mnt # Unmount the file system mounted at /mnt
fstab
# File system table (configuration file for mounting file systems)
# /etc/fstab : View and configure persistent mount points
# Example:
cat /etc/fstab # View fstab configuration
blkid
# Display block device attributes
# Example:
blkid # Show attributes of all block devices
fsck [options] [device]
# Check and repair a file system
# Example:
fsck /dev/sda1 # Check and repair /dev/sda1 20. Filesystem Permissions and Security
# Filesystem Permissions and Security
chmod [options] [permissions] [file]
# Change file permissions
# Example:
chmod 755 file.txt # Give read, write, and execute permissions to owner, and read-execute permissions to others
chown [options] [owner][:group] [file]
# Change file owner and group
# Example:
chown user:group file.txt # Change owner and group of a file
chgrp [options] [group] [file]
# Change group ownership of a file
# Example:
chgrp group file.txt # Change the group of a file
umask [permissions]
# Set default permissions for new files
# Example:
umask 022 # Set default permissions for newly created files to 755
setfacl [options] [file]
# Set access control lists (ACL) for file permissions
# Example:
setfacl -m u:user:rwx file.txt # Set ACL to give 'user' read, write, execute permissions
getfacl [file]
# Get access control lists (ACL) for file permissions
# Example:
getfacl file.txt # View ACL for a file 21. Containerization and Orchestration
Docker
docker [options] [command]
# Docker command-line interface (CLI) for managing containers
docker run [options] <image>
# Run a container from an image
# Example:
docker run ubuntu # Run a container from the Ubuntu image
docker ps [options]
# List running containers
# Example:
docker ps # List all running containers
docker ps -a [options]
# List all containers, including stopped ones
# Example:
docker ps -a # List all containers
docker build -t <image_name> .
# Build an image from a Dockerfile
# Example:
docker build -t my-image . # Build an image named 'my-image' from the Dockerfile in the current directory
docker exec -it <container_id> bash
# Start an interactive bash shell inside a running container
# Example:
docker exec -it container_id bash # Access bash shell in a running container
docker stop <container_id>
# Stop a container
# Example:
docker stop container_id # Stop the container with the specified ID
docker rm <container_id>
# Remove a container
# Example:
docker rm container_id # Remove the specified container
docker logs <container_id>
# View logs of a container
# Example:
docker logs container_id # View logs from the container
docker images [options]
# List available images
# Example:
docker images # List all Docker images
docker rmi <image_name>
# Remove an image
# Example:
docker rmi my-image # Remove the 'my-image' image
docker network ls
# List Docker networks
# Example:
docker network ls # List all Docker networks
docker-compose [options]
# Manage multi-container Docker applications
docker-compose up [options]
# Start up a multi-container environment
# Example:
docker-compose up # Start up the environment defined in the docker-compose.yml file
docker-compose down [options]
# Stop and remove containers created by docker-compose
# Example:
docker-compose down # Stop and remove the containers
docker-compose logs [options]
# View logs from containers managed by docker-compose
# Example:
docker-compose logs # View logs from containers in the docker-compose environment Kubernetes (k8s)
# Kubernetes (k8s)
kubectl [options] [command]
# Command-line tool for interacting with Kubernetes clusters
kubectl get pods [options]
# List pods in the current namespace
# Example:
kubectl get pods # List all pods in the current namespace
kubectl get nodes [options]
# List nodes in the cluster
# Example:
kubectl get nodes # List all nodes in the cluster
kubectl get services [options]
# List services in the cluster
# Example:
kubectl get services # List all services in the cluster
kubectl apply -f <file>.yaml [options]
# Apply configuration from a file (e.g., a deployment or pod configuration)
# Example:
kubectl apply -f deployment.yaml # Apply configuration from the deployment.yaml file
kubectl create -f <file>.yaml [options]
# Create a resource from a file
# Example:
kubectl create -f pod.yaml # Create a pod from the pod.yaml file
kubectl delete -f <file>.yaml [options]
# Delete a resource defined in a file
# Example:
kubectl delete -f service.yaml # Delete the service defined in service.yaml
kubectl exec -it <pod_name> -- bash
# Execute a command inside a pod (e.g., open a shell)
# Example:
kubectl exec -it my-pod -- bash # Open a bash shell inside the 'my-pod' pod
kubectl logs <pod_name>
# View the logs of a pod
# Example:
kubectl logs my-pod # View logs of the 'my-pod' pod
kubectl describe pod <pod_name>
# Get detailed information about a pod
# Example:
kubectl describe pod my-pod # Get detailed information about the 'my-pod' pod
kubectl scale deployment <deployment_name> --replicas=<number>
# Scale a deployment to the desired number of replicas
# Example:
kubectl scale deployment my-deployment --replicas=3 # Scale 'my-deployment' to 3 replicas
kubectl rollout restart deployment <deployment_name>
# Restart a deployment
# Example:
kubectl rollout restart deployment my-deployment # Restart the 'my-deployment' deployment
kubectl port-forward pod <pod_name> <local_port>:<remote_port>
# Forward a port from a pod to localhost
# Example:
kubectl port-forward pod my-pod 8080:80 # Forward port 80 from 'my-pod' to local port 8080Helm – Kubernetes package manager for deploying applications
# Helm - Kubernetes package manager for deploying applications
helm [options] [command]
# Helm CLI for managing Kubernetes applications
helm install <release_name> <chart_name> [options]
# Install a Helm chart
# Example:
helm install my-release stable/mysql # Install the 'mysql' chart with the release name 'my-release'
helm upgrade <release_name> <chart_name> [options]
# Upgrade a Helm release
# Example:
helm upgrade my-release stable/mysql # Upgrade the 'my-release' release to the latest 'mysql' chart version
helm list [options]
# List all Helm releases
# Example:
helm list # List all the installed Helm releases
helm delete <release_name> [options]
# Delete a Helm release
# Example:
helm delete my-release # Delete the 'my-release' Helm release
helm search <chart_name> [options]
# Search for a Helm chart
# Example:
helm search mysql # Search for Helm charts related to 'mysql'Ansible
ansible [options] [command]
# Ansible CLI for automation and configuration management
ansible all -m ping
# Ping all hosts defined in the inventory
# Example:
ansible all -m ping # Test connectivity to all hosts
ansible-playbook playbook.yml
# Run an Ansible playbook
# Example:
ansible-playbook deploy_app.yml # Execute the specified playbook
ansible -m command -a 'command' <host>
# Run a single command on a target host
# Example:
ansible -m command -a 'uptime' server01 # Run 'uptime' on 'server01'
ansible-playbook --check playbook.yml
# Dry-run a playbook to see what would change
# Example:
ansible-playbook --check deploy_app.yml # Preview changes without actually applying
ansible-playbook --limit <host> playbook.yml
# Run a playbook on a specific host or group
# Example:
ansible-playbook --limit server01 deploy_app.yml # Run the playbook only on 'server01'
ansible-playbook --extra-vars "key=value"
# Pass extra variables to a playbook
# Example:
ansible-playbook -e "env=production" deploy_app.yml # Pass 'env=production' to the playbookTerraform
terraform [options] [command]
# Terraform CLI for infrastructure as code
terraform init
# Initialize a working directory for Terraform configuration
# Example:
terraform init # Initialize the directory containing Terraform configuration files
terraform plan
# Show an execution plan (preview of what changes will be made)
# Example:
terraform plan # Preview the changes that will be made to infrastructure
terraform apply
# Apply the changes described in a Terraform configuration
# Example:
terraform apply # Apply the planned changes to infrastructure
terraform destroy
# Destroy infrastructure created by Terraform
# Example:
terraform destroy # Destroy all infrastructure managed by Terraform
terraform validate
# Validate the configuration files
# Example:
terraform validate # Check for any syntax or logical errors in Terraform files
terraform show
# Show the current state of the infrastructure
# Example:
terraform show # Display the current infrastructure statePuppet
puppet [options] [command]
# Puppet CLI for configuration management
puppet apply <manifest.pp>
# Apply a Puppet manifest locally
# Example:
puppet apply site.pp # Apply the local Puppet manifest 'site.pp'
puppet agent --test
# Test the Puppet agent (can be used to run a one-off run)
# Example:
puppet agent --test # Run a one-time agent run for configuration management
puppet resource
# Show the current state of resources (files, services, etc.)
# Example:
puppet resource service apache # Show the current state of the Apache service22. CI / CD Tool and Commands
Jenkins
java -jar jenkins.war
# Start Jenkins from a WAR file
# Example:
java -jar jenkins.war # Launch Jenkins server from the 'jenkins.war' file
# Access Jenkins through http://localhost:8080 by defaultGitLab CI
.gitlab-ci.yml
# Configuration file for GitLab CI/CD pipelines (typically resides in your repository)
# Example:
# .gitlab-ci.yml file defines the pipeline stages and jobs
gitlab-runner register
# Register a new runner with GitLab
# Example:
gitlab-runner register --url https://gitlab.com/ --registration-token <token> # Register a runner
gitlab-runner run
# Run the GitLab Runner to process jobs
# Example:
gitlab-runner run # Run the registered runner to execute jobsGitHub Actions
# GitHub Actions uses YAML configuration files (typically located in .github/workflows/)
# Example of GitHub Action YAML file:
name: CI Pipeline
on:
push:
branches: [main]
jobs:
build:
runs-on: ubuntu-latest
steps:
- name: Checkout code
uses: actions/checkout@v2 # Checkout the repository code in your CI pipeline
- name: Setup Node.js
uses: actions/setup-node@v2 # Setup Node.js for use in a pipeline
- name: Set up Docker Buildx
uses: docker/setup-buildx-action@v1 # Set up Docker Buildx for building multi-platform images23. Cloud Services
AWS CLI
aws [service] [operation] [options]
# Command-line tool for managing AWS services
aws configure
# Configure AWS CLI with your credentials
# Example:
aws configure # Set up AWS access credentials (Access Key, Secret Key, region)
aws s3 cp file.txt s3://bucket-name/
# Copy a file to an S3 bucket
# Example:
aws s3 cp file.txt s3://my-bucket/ # Upload 'file.txt' to S3 bucket
aws ec2 describe-instances
# Describe EC2 instances
# Example:
aws ec2 describe-instances # Get details of EC2 instances
aws ec2 start-instances --instance-ids <id>
# Start an EC2 instance
# Example:
aws ec2 start-instances --instance-ids i-0123456789abcde # Start an EC2 instance with the given ID
aws ec2 stop-instances --instance-ids <id>
# Stop an EC2 instance
# Example:
aws ec2 stop-instances --instance-ids i-0123456789abcde # Stop an EC2 instance with the given ID
aws s3 sync
# Sync directories with an S3 bucket
# Example:
aws s3 sync /local/directory/ s3://my-bucket/ # Sync local directory to S3 bucketAzure CLI
az [service] [operation] [options]
# Command-line tool for managing Azure services
az login
# Log in to your Azure account
# Example:
az login # Log in to Azure
az vm list
# List all virtual machines
# Example:
az vm list # Get a list of all VMs in Azure
az vm start --name <vm_name> --resource-group <resource_group>
# Start an Azure VM
# Example:
az vm start --name myVM --resource-group myResourceGroup # Start a VM named 'myVM'
az storage blob upload
# Upload files to an Azure blob storage
# Example:
az storage blob upload --container-name mycontainer --file file.txt --name file.txt # Upload file to Azure blob storage
az group create
# Create a new resource group in Azure
# Example:
az group create --name myResourceGroup --location eastus # Create a new resource groupGoogle Cloud SDK (gcloud)
gcloud [service] [operation] [options]
# Command-line tool for Google Cloud Platform
gcloud auth login
# Log in to Google Cloud
# Example:
gcloud auth login # Log in to your Google Cloud account
gcloud compute instances list
# List compute instances
# Example:
gcloud compute instances list # Get a list of VM instances in Google Cloud
gcloud compute instances stop <instance_name>
# Stop a Google Cloud VM instance
# Example:
gcloud compute instances stop my-instance # Stop the VM 'my-instance'
gcloud app browse
# Open the current Google App Engine application in a browser
# Example:
gcloud app browse # Open the app hosted in Google Cloud24. Logging and Monitoring
Prometheus (System Monitoring and Alerting Toolkit)
prometheus
# Start Prometheus server (usually runs as a service in the background)
# Example:
prometheus # Starts Prometheus monitoring system
prometheus --config.file=<config_file>
# Start Prometheus with a specific config file
# Example:
prometheus --config.file=/etc/prometheus/prometheus.yml # Run Prometheus with custom configuration fileGrafana (Open-Source Data Visualization)
grafana-cli
# Command-line interface for managing Grafana plugins
grafana-cli plugins install <plugin-name>
# Install a plugin in Grafana
# Example:
grafana-cli plugins install grafana-clock-panel # Install Grafana clock panel pluginELK Stack (Elasticsearch, Logstash, Kibana)
Elasticsearch (Search Engine for Logging and Data Analytics)
curl -XGET 'localhost:9200/_cluster/health?pretty'
# Get cluster health status
# Example:
curl -XGET 'localhost:9200/_cluster/health?pretty' # Check the health of your Elasticsearch clusterLogstash (Server-Side Data Processing Pipeline)
logstash -f <config_file>
# Run Logstash with the specified configuration file
# Example:
logstash -f /etc/logstash/conf.d/logstash.conf # Run Logstash with a specific configuration fileKibana (Web Interface for Visualizing Elasticsearch Data)
# Kibana is generally accessed through a web browser
# Access Kibana interface at:
http://localhost:5601
# Example:
# Open Kibana dashboard in the web browser to visualize data
