Search

• search for string in files recursively

grep -R "Suchstring" *

•  search for string in stdout

cat /var/log/syslog | grep 'ERROR'

•  count lines in output

cat /var/log/syslog | grep 'ERROR' -c

• search for a file recursively

find . -iname "settings.py"

• search and replace string in multiple files (replace bike with car in all html files in this folder)

find . -iname "*.html" -depth 1 -exec sed -i "" -e "s/car/bike/g" {} \;

User management

• add user to a group

addgroup USER GRUPPE

Process management

• show applications and ports they opened

netstat -tulpn