Linux cheat sheet

ls -lah
ls -lah /etc

find . -name "*.py"
find /var -mtime -7 -type f  # modificati negli ultimi 7gg
find . -size +10M

cp file.txt backup.txt
cp -r src/ dst/

mv old.txt new.txt
mv *.log /var/logs/

rm file.txt
rm -rf ./tmpdir

mkdir -p /opt/myapp/logs

ln -s /opt/myapp /usr/local/bin/myapp

du -sh /var/log
du -sh * | sort -h  # ordina per dimensione

cat /etc/hosts
cat file1 file2 > merged.txt

grep -rn "TODO" ./src
grep -v "^#" config.txt  # escludi commenti
grep -E "error|warn" app.log

sed 's/http/https/g' urls.txt
sed -i 's/foo/bar/g' file.txt  # in-place

awk '{print $1, $3}' data.txt
awk -F: '{print $1}' /etc/passwd  # lista utenti

sort file.txt
sort -k2 -n data.txt
sort -u file.txt  # rimuovi duplicati

cut -d: -f1 /etc/passwd
cut -d',' -f2,4 data.csv

tail -100 app.log
tail -f /var/log/syslog

wc -l access.log
grep "ERROR" app.log | wc -l

ps aux
ps aux | grep nginx

top
top -u www-data  # filtra per utente

kill -9 1234  # SIGKILL: forza termina
kill -15 1234  # SIGTERM: chiudi pulito

killall nginx

nohup python3 server.py &
nohup ./script.sh > out.log 2>&1 &

jobs
bg %1  # manda in background
fg %1  # riporta in foreground

chmod 755 script.sh
chmod +x deploy.sh
find /var/www/html -type d -exec chmod 755 {} \;
find /var/www/html -type f -exec chmod 644 {} \;

chown www-data:www-data /var/www
chown -R enzo:enzo /opt/myapp

sudo apt update
sudo -u postgres psql  # come altro utente

sudo visudo

curl -X GET https://api.example.com/users
curl -X POST -H "Content-Type: application/json" -d '{"k":"v"}' <url>
curl -O https://example.com/file.zip

ssh enzo@192.168.1.100
ssh -i ~/.ssh/id_rsa user@server
ssh -L 8080:localhost:80 user@server  # tunnel

scp file.txt enzo@server:/home/enzo/
scp -r ./dist user@server:/var/www/

ss -tulnp
ss -tulnp | grep 8080

ip addr
ip addr show eth0

ping -c 4 google.com
ping -c 1 192.168.1.1

df -h
df -h /var

lsblk
lsblk -f  # includi filesystem

# crea
tar -czf backup.tar.gz /opt/myapp
# estrai
tar -xzf backup.tar.gz -C /tmp
# visualizza contenuto
tar -tzf backup.tar.gz

rsync -avz ./dist/ user@server:/var/www/
rsync -avz --delete src/ dst/

uname -a

uptime
uptime -p  # human-readable

systemctl start nginx
systemctl enable nginx
systemctl status nginx
systemctl restart nginx

journalctl -u nginx -f
journalctl -u nginx --since "1 hour ago"

env
env | grep PATH

export NODE_ENV=production
export PATH="$PATH:/opt/myapp/bin"

# formato: min ora giorno mese dow comando
0 2 * * * /opt/backup.sh  # ogni notte alle 2:00
*/5 * * * * /opt/check.sh  # ogni 5 minuti