Added a basic guide on migrating to another server

docs/installing.md

@@ -39,3 +39,4 @@ Now that the services are running, you might want to:
 - or [set up the Dimension Integrations Manager](configuring-playbook-dimension.md)
 - or [check if services work](maintenance-checking-services.md)
 - or learn how to [upgrade your services when new versions are released](maintenance-upgrading-services.md)
+- or learn how to [migrate to another server](maintenance-migrating.md)

docs/maintenance-migrating.md

@@ -0,0 +1,7 @@
+# Migrating to new server
+
+1. Backup directory `/matrix`. Make sure to preserve owner and permission (use `cp -p`)!
+2. Remove old server from matrix-docker-ansible-deploy `hosts` file and add new server.
+3. Run `ansible-playbook -i inventory/hosts setup.yml --tags=setup-all`. This will create the matrix user and group.
+4. Copy backup from old server to new server. Make sure to preserve owner and permission (use `cp -p`)!
+5. Run `ansible-playbook -i inventory/hosts setup.yml --tags=start`