First bit of configuration of coturn added.

matrix/coturn/README.md

@@ -0,0 +1,43 @@
+---
+gitea: none
+include_toc: true
+---
+
+# TURN server
+
+You need an TURN server to connect participants that are behind a NAT firewall.
+
+Installation is short:
+
+```
+apt install coturn
+```
+
+For sake of maintainability we'll move the only configuration file into its
+own directoy:
+
+```
+mkdir /etc/coturn
+mv /etc/turnserver.conf /etc/coturn
+```
+
+We need to tell systemd to start it with the configuration file on the new
+place. Edit the service file with:
+
+```
+systemctl edit coturn
+```
+
+Contrary to what the comment suggests, only the parts you add will override
+the content that's already there. We have to "clean" the `ExecStart` first,
+before we assign a new line to it, so this is the bit we add:
+
+```
+[Service]
+ExecStart=
+ExecStart=/usr/bin/turnserver -c /etc/coturn/turnserver.conf --pidfile=
+```
+
+This takes care of the configuration file. Now, the configuration itself...
+
+