I am constantly having to use these commands when administering remote systems. I’ll just put them in one place for future reference.

Change all directories and subdirectories to a specific user and group find . -type d -exec chown user:group {} +

Change all files in the current directory and all subdirectories to a specific user and group find . -type f -exec chown user:group {} +

Setting the time zone dpkg-reconfigure tzdata

Generate a 4096 byte SSH key ssh-keygen -t rsa -b 4096 -f id_rsa_user -C user