Linux Commands Cheat Sheet

pwd                    # print working directory
ls -la                 # list all with details
cd /var/log            # change directory
cd ~                   # home directory
cd -                   # previous directory

mkdir -p src/components   # create nested dirs
touch file.txt            # create empty file
rm file.txt               # remove file
rm -rf directory/         # remove dir recursively

cp file.txt backup.txt
cp -r src/ src-backup/
mv old.txt new.txt         # rename
mv file.txt /tmp/          # move

find . -name '*.log'
find /var -size +100M
find . -mtime -7 -name '*.py'

cat file.txt
less file.txt             # paginated
head -20 file.txt         # first 20 lines
tail -50 file.txt         # last 50 lines
tail -f /var/log/app.log  # follow in real-time

grep 'error' app.log
grep -r 'TODO' src/        # recursive
grep -i 'warning' log.txt  # case-insensitive
grep -c 'error' app.log    # count matches

sort file.txt | uniq       # unique sorted lines
wc -l file.txt             # count lines
cut -d',' -f1,3 data.csv   # extract columns
sed 's/old/new/g' file.txt # find and replace

chmod 755 script.sh        # rwxr-xr-x
chmod +x script.sh         # add execute
chmod -R 644 docs/         # recursive

chown user:group file.txt
chown -R www-data:www-data /var/www/

# r=4  w=2  x=1
# 755 = rwxr-xr-x (owner:all, group:rx, other:rx)
# 644 = rw-r--r-- (owner:rw, group:r, other:r)
# 700 = rwx------ (owner only)

ps aux                     # all processes
ps aux | grep node         # filter
top                        # real-time
htop                       # interactive (if installed)

kill 1234                  # graceful stop (SIGTERM)
kill -9 1234               # force kill (SIGKILL)
killall node               # kill by name

command &                  # run in background
nohup command &            # survives terminal close
jobs                       # list background jobs
fg %1                      # bring job 1 to foreground

ping google.com
curl -I https://example.com    # headers only
curl -X POST -d '{"a":1}' -H 'Content-Type: application/json' url
wget https://example.com/file.tar.gz

ss -tlnp                   # listening TCP ports
netstat -tlnp              # alternative
lsof -i :3000              # what's using port 3000

dig example.com
nslookup example.com
host example.com

df -h                      # filesystem usage
du -sh *                   # directory sizes
du -sh /var/log             # specific directory
ncdu /                     # interactive (if installed)

free -h                    # RAM usage
vmstat 1                   # virtual memory stats

tar -czf archive.tar.gz src/   # create gzipped
tar -xzf archive.tar.gz        # extract gzipped
tar -tf archive.tar.gz         # list contents

zip -r archive.zip src/
unzip archive.zip

command > out.txt          # overwrite
command >> out.txt         # append
command 2>&1               # stderr to stdout
command1 | command2        # pipe

find . -name '*.log' | xargs rm
cat urls.txt | xargs -I {} curl {}

watch -n 5 'df -h'         # run every 5 seconds