Disk: df -h (freier/belegter Platz)
Display resolution: xrandr -s <width in px>x<height in px> (may require restart of window manager, e.g. fvwm)
HTTP Proxy: export http_proxy=http://<host>:<port>
Keyboard layout: dpgk-reconfigure console-data (Konsole), setxkbmap -layout de -variant nodeadkeys (X), edit /etc/X11/xorg.conf (X)
Locale: Set locale as non root user: edit ~/.bashrc. Add e.g. the following line: export LANG=de_DE.UTF-8 (German, UTF-8)
Package: dpkg -L <package name> (Lists all installed files of a deb package)
Users: List all currently logged in users: “users” or “who”
Zeit und Datum stellen, zum Beispiel: date -s “1 SEP 2010 18:00:00”