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Linux Commands Reference

Quick reference for essential Linux/Unix commands: file management, text processing, processes, networking, and more.

File & Directory

ls -laList files with details and hidden files
cd <dir>Change directory
pwdPrint working directory
mkdir -p <dir>Create directory (and parents)
rm -rf <dir>Remove directory recursively (careful!)
cp -r <src> <dest>Copy files/directories recursively
mv <src> <dest>Move or rename file/directory
touch <file>Create empty file or update timestamp
find . -name "*.txt"Find files by name pattern
find . -type f -size +10MFind files larger than 10MB
du -sh *Show disk usage of each item
df -hShow disk space usage

Text Processing

cat <file>Print file contents
less <file>Page through file (q to quit)
head -n 20 <file>Show first 20 lines
tail -n 20 <file>Show last 20 lines
tail -f <file>Follow file (live log viewing)
grep -r "pattern" .Search for pattern recursively
grep -i "pattern" <file>Case-insensitive search
grep -n "pattern" <file>Show line numbers in results
sed -i "s/old/new/g" <file>Replace text in file in-place
awk '{print $1}' <file>Print first column
sort <file>Sort lines alphabetically
sort -n -k2 <file>Sort numerically by 2nd column
uniq -cCount and deduplicate adjacent lines
wc -l <file>Count lines in file
cut -d"," -f1,3 <file>Cut specific columns (CSV)

Processes

ps auxList all running processes
topInteractive process viewer
htopEnhanced process viewer (if installed)
kill <pid>Terminate process by PID
kill -9 <pid>Force kill process
pkill <name>Kill processes by name
pgrep <name>Find PIDs by process name
nohup <cmd> &Run command immune to hangups, in background
jobsList background jobs
bg %1Resume job 1 in background
fg %1Bring job 1 to foreground

Permissions & Ownership

chmod 755 <file>Set rwxr-xr-x permissions
chmod +x <file>Make file executable
chown user:group <file>Change file owner and group
sudo <cmd>Run command as superuser
sudo -iSwitch to root shell
su - <user>Switch to another user
umask 022Set default permission mask

Networking

curl -I <url>Show response headers only
curl -L -o file <url>Download file following redirects
wget <url>Download file
ping <host>Test network connectivity
traceroute <host>Trace network path to host
nslookup <domain>DNS lookup
dig <domain>Detailed DNS lookup
netstat -tulnShow listening ports
ss -tulnShow listening ports (modern)
ssh user@hostConnect via SSH
scp <file> user@host:/pathCopy file via SSH
rsync -avz src/ user@host:dest/Sync files efficiently

Archives & Compression

tar -czf archive.tar.gz <dir>Create gzip compressed archive
tar -xzf archive.tar.gzExtract gzip archive
tar -cjf archive.tar.bz2 <dir>Create bzip2 compressed archive
zip -r archive.zip <dir>Create zip archive
unzip archive.zipExtract zip archive
gzip <file>Compress file with gzip
gunzip <file>.gzDecompress gzip file

System Info

uname -aSystem and kernel information
cat /etc/os-releaseOS version information
free -hMemory usage
uptimeSystem uptime and load
whoWho is logged in
idCurrent user and group IDs
envShow environment variables
export VAR=valueSet environment variable
which <cmd>Find command path
historyCommand history
man <cmd>Manual page for a command

About This Tool

The Linux Commands Reference provides a curated collection of essential Linux/Unix commands organized into seven categories: file and directory management, text processing, process control, permissions and ownership, networking, archives and compression, and system information.

Each command includes a real-world usage example and a concise description. Use the search box to quickly filter commands by name or description keyword.

How to Use

  1. Type a command name or keyword into the search box.
  2. Scroll through categories to browse commands.
  3. Review the command and description, then use it in your terminal.
  4. Replace angle-bracketed placeholders (<dir>, <file>, etc.) with actual values.

Use Cases

DevOps engineers writing deployment scripts, sysadmins debugging server issues, developers checking file permissions or processes, and beginners learning Linux command-line fundamentals.

FAQ

  • What do the angle brackets (<>) mean? Angle brackets are placeholders. Replace <dir> with an actual directory path, <file> with a filename, <pid> with a process ID, and so on.
  • What if a command is not found? Some commands like htop are not installed by default. Install them with your package manager (e.g., sudo apt install htop) or verify availability with the man command.
  • What should I be careful about with sudo? sudo runs commands with superuser privileges. Destructive commands like rm -rf used with sudo can cause irreversible data loss. Always double-check before executing.