Common Linux Commands Reference

uname -a               # Display kernel version, OS, and CPU architecture
head -n 1 /etc/issue   # View operating system version
env                    # List all environment variables

# Check CentOS version
cat /etc/redhat-release

# CPU details
cat /proc/cpuinfo

# Memory details
cat /proc/meminfo

# Update system timezone
timedatectl set-timezone Asia/Shanghai

# Search for a specific process using ps and grep
$ ps aux | grep <process_name>

# Change the current user's password
passwd

# Show who is logged on and what they are doing
w

# List file attributes, owners, and groups
ls -l

# Change file group
chgrp [-R] groupname filename

# Change file owner (and optionally the group)
chown [-R] ownername filename
chown [-R] owner:group filename

# Remove a file
rm filename

# Remove a directory and its contents recursively
rm -rf dirname

# Find and delete specific files/folders
find . -name "test" | xargs rm -rf   

# Copy a file
cp config.conf config.conf.bak

# Rename or move a file
mv old.txt new.txt

# Move all files from a subdirectory to the current directory
mv ./temp/deploy/* .

# List all files (including hidden) in long format
ls -Al

# List a specific range of files (e.g., 101st to 200th)
ls | sort -n | head -200 | tail -100

# Extract a zip archive
unzip archive.zip

# Create a compressed tarball
tar zcvf archive.tar.gz dirname/

# Extract a tarball
tar zxvf archive.tar.gz

chkconfig --list           # List all system services
chkconfig mysqld on        # Enable a service at boot

service nginx start        # Start a service
systemctl status nginx     # Check service status (modern Linux)

# Download a file or view source code
curl https://example.com >> index.html

# Send a cookie with a request
curl --cookie "session=123" https://example.com

# Local port forwarding (tunneling)
ssh -p 22 -L <localPort>:localhost:<serverPort> user@remote_host

# Execute a command on a remote server (using sshpass for automated scripts)
sshpass -p 'password' ssh user@host "ls -la"

# Find the absolute path of a command
which python

# Display a specific environment variable
echo $NODE_ENV

# Set an environment variable for the current session
export NODE_ENV="production"

# Remove an environment variable
unset NODE_ENV

# View disk space in human-readable format
df -h

# View memory usage in MB
free -m

# Check which process is using a specific port
lsof -i:8080

# Forcefully terminate a process by PID
kill -9 <pid>