List of the most useful Ubuntu administration commands.
Package Management
Find out what packages if any use the specified folder,
dpkg -S "/etc/ssl/certs" openssl, ca-certificates: /etc/ssl/certs
List all files relate to a package,
dpkg -L ca-certificates /. /etc /etc/ssl /etc/ssl/certs /etc/ca-certificates /etc/ca-certificates/update.d /usr /usr/sbin /usr/sbin/update-ca-certificates /usr/share /usr/share/ca-certificates ...