dhcpcd to manage networks. Despite the name this does more than allocate addresses; it can actively switch between networks and interfaces, and repair broken connections.
wpasupplicant to provide details of known wireless networks (and other optional settings). (
dhcpcd can directly call
wpasupplicant, but Raspbian Jessie omitted the hook to do this, although this is included in Stretch and Buster.)
How do I set up networking/WiFi/Static IP
etc/network/interfaces is used by used by ifup and ifdown.
It can be used to provide a simple static setup, which can be managed manually. The default works with
One disadvantage of putting wireless settings in interfaces (apart from lack of flexibility) is that any user can read password.