update documentation

README.md

@@ -68,6 +68,8 @@ Some of the following instructions must be executed with `root` privileges.
    chroot debian-sid/ /debootstrap/debootstrap --second-stage
    ```
 
+   Note: Without `--variant=minbase`, sound won't work for some strange, unknown reason.
+
 3. Install `linphone-cli` inside the chroot environment
 
    ```
@@ -90,7 +92,13 @@ Some of the following instructions must be executed with `root` privileges.
    mount -a
    ```
 
-6. Configure and enable `linphone-daemon` as `systemd` service
+6. Copy *Linphone* configuration file
+
+   ```
+   cp linphone.conf /var/tmp/debian-sid/home/pi/
+   ```
+
+7. Configure and enable `linphone-daemon` as `systemd` service
 
    ```
    ln -sr linphone-daemon.service /etc/systemd/system
@@ -98,10 +106,22 @@ Some of the following instructions must be executed with `root` privileges.
    systemctl enable linphone-daemon
    ```
 
+
 ## Configuring `fetapd`
 
 :warning: TODO
 
+### Identifying soundcard
+
+```
+# chroot /var/tmp/debian-sid /usr/bin/linphonec
+...
+linphonec> soundcard list
+0: ALSA: default
+1: ALSA: bcm2835 Headphones
+2: ALSA: C-Media USB Headphone Set
+```
+
 ## Starting `fetapd`
 
 ```