How to delete files older than …

find PATH TO FILES GOES HERE* -mtime +5 -exec COMMAND GOES HERE {} \;

Raspberry Pi Debian – How to change swap size

sudo nano /etc/dphys-swapfile
sudo dphys-swapfile setup
sudo dphys-swapfile swapon


Linux – how to check which process is using most memory

ps -elf|awk '{print $10, $3, $4, $15, $16}'|sort -nr|head