I would like to take a Raspberry Pi to a place and plug it into an amp connected to some speakers. It runs Debian with mpd and allows us to play all the music on it. Now: at home, it is connected to the router with /etc/network/interfaces.d/wlan0 providing wpa-ssid and wpa-psk. This works. But now, at the other place, there is no router. The Raspberry Pi still has a network card. How can I turn it into a "server" so that it provides a wireless network which I can pick on my phone? It probably also needs some sort of DNS? Is there an URL explaining how to do this somewhere?