Added support for sound.

README.md

@@ -37,6 +37,7 @@ Mozilla Firefox is a free and open-source web browser developed by Mozilla Found
          * [Routing Based on Hostname](#routing-based-on-hostname)
          * [Routing Based on URL Path](#routing-based-on-url-path)
       * [Increasing Shared Memory Size](#increasing-shared-memory-size)
+      * [Sound Support](#sound-support)
       * [Troubleshooting](#troubleshooting)
          * [Crashes](#crashes)
       * [Support or Contact](#support-or-contact)
@@ -434,6 +435,12 @@ size of `/dev/shm` can be done via two method:
   - By using shared memory of the host, by mapping `/dev/shm` via the parameter
     `-v /dev/shm:/dev/shm` of the `docker run` command.
 
+## Sound Support
+
+For Firefox to be able to use the audio device available on
+the host, `/dev/snd` must be exposed to the container by adding the
+`--device /dev/snd` parameter to the `docker run` command.
+
 ## Troubleshooting
 
 ### Crashes

appdefs.xml

@@ -41,6 +41,14 @@ size of `/dev/shm` can be done via two method:
     `-v /dev/shm:/dev/shm` of the `docker run` command.
         </content>
       </section>
+    <section>
+      <title level="2">Sound Support</title>
+      <content>
+For {{ defs.app.friendly_name }} to be able to use the audio device available on
+the host, `/dev/snd` must be exposed to the container by adding the
+`--device /dev/snd` parameter to the `docker run` command.
+      </content>
+    </section>
       <section>
         <title level="2">Troubleshooting</title>
         <content/>
@@ -100,7 +108,13 @@ details.
     <!-- Network ports -->
     <ports/>
     <!-- Devices -->
-    <devices/>
+    <devices>
+      <device>
+        <path>/dev/snd</path>
+        <description>Optional Linux device to expose to have sound.</description>
+        <include_in_quick_start>false</include_in_quick_start>
+      </device>
+    </devices>
     <!-- Extra parameters -->
     <extra_params>
       <extra_param>

rootfs/etc/cont-init.d/check-snd.sh

@@ -0,0 +1,25 @@
+#!/usr/bin/with-contenv sh
+
+set -e # Exit immediately if a command exits with a non-zero status.
+set -u # Treat unset variables as an error.
+
+log() {
+    echo "[cont-init.d] $(basename $0): $*"
+}
+
+SND_DEV="/dev/snd"
+
+if [ ! -d "$SND_DEV" ]; then
+    log "sound not supported: device $SND_DEV not exposed to the container."
+    exit 0
+fi
+
+# Save the associated group.
+SND_GRP="$(find "$SND_DEV" -maxdepth 1 -not -type d -exec stat -c "%g" {} \; | sort -u | tail -n1)"
+log "sound device group $SND_GRP."
+if [ -f /var/run/s6/container_environment/SUP_GROUP_IDS ]; then
+    echo -n "," >> /var/run/s6/container_environment/SUP_GROUP_IDS
+fi
+echo -n "$SND_GRP" >> /var/run/s6/container_environment/SUP_GROUP_IDS
+
+# vim: set ft=sh :