diff --git a/openvidu-server/docker/openvidu-recording/firefox/Dockerfile b/openvidu-server/docker/openvidu-recording/firefox/Dockerfile
index d4ccaebe..98a6fcb1 100644
--- a/openvidu-server/docker/openvidu-recording/firefox/Dockerfile
+++ b/openvidu-server/docker/openvidu-recording/firefox/Dockerfile
@@ -1,21 +1,24 @@
-FROM ubuntu:16.04
+FROM ubuntu:20.04
 MAINTAINER openvidu@gmail.com
 
+# Install packages
+RUN apt-get update && apt-get -y upgrade && apt-get install -y \
+    wget \
+    sudo \
+    gnupg2 \
+    apt-utils \
+    software-properties-common \
+    ffmpeg \
+    pulseaudio \
+    xvfb \
+    jq \
+  && rm -rf /var/lib/apt/lists/*
+
 # Install Firefox
-RUN apt-get update && apt-get -y upgrade && apt-get install -y wget sudo
-RUN apt-get install -y firefox
+RUN apt-get update && apt-get -y upgrade && apt-get install -y firefox
 
-# Install media packages
-RUN apt-get install -y software-properties-common
-RUN add-apt-repository ppa:jonathonf/ffmpeg-4
-RUN apt-get update
-RUN apt-get install -y ffmpeg pulseaudio xvfb
-
-# Install jq for managing JSON
-RUN apt-get install -y jq
-
-# Clean
-RUN apt-get autoclean
+# Clean	
+RUN apt-get clean && apt-get autoclean && apt-get autoremove
 
 COPY entrypoint.sh /entrypoint.sh
 COPY configuration/autoconfig.js /usr/lib/firefox/defaults/pref/autoconfig.js
diff --git a/openvidu-server/docker/openvidu-recording/firefox/configuration/customconfig.cfg b/openvidu-server/docker/openvidu-recording/firefox/configuration/customconfig.cfg
index 3aac4941..173433b0 100644
--- a/openvidu-server/docker/openvidu-recording/firefox/configuration/customconfig.cfg
+++ b/openvidu-server/docker/openvidu-recording/firefox/configuration/customconfig.cfg
@@ -5,4 +5,6 @@ lockPref("extensions.autoDisableScopes", 0);
 lockPref("extensions.enabledScopes", 15);
 lockPref("security.ssl.enable_ocsp_stapling", false);
 lockPref("network.stricttransportsecurity.preloadlist", false);
-lockPref("network.http.phishy-userpass-length", 300);
\ No newline at end of file
+lockPref("network.http.phishy-userpass-length", 300);
+lockPref("security.enterprise_roots.enabled", true);
+lockPref("network.websocket.allowInsecureFromHTTPS", true);
\ No newline at end of file
diff --git a/openvidu-server/docker/openvidu-recording/firefox/create_image.sh b/openvidu-server/docker/openvidu-recording/firefox/create_image.sh
index beb53402..a7caa7af 100755
--- a/openvidu-server/docker/openvidu-recording/firefox/create_image.sh
+++ b/openvidu-server/docker/openvidu-recording/firefox/create_image.sh
@@ -1 +1 @@
-docker build --rm -t openvidu/openvidu-recording:2.10.0-firefox .
+docker build --rm -t openvidu/openvidu-recording:2.15.0-firefox .
diff --git a/openvidu-server/docker/openvidu-recording/firefox/entrypoint.sh b/openvidu-server/docker/openvidu-recording/firefox/entrypoint.sh
index 5732cfe7..4a59f02e 100755
--- a/openvidu-server/docker/openvidu-recording/firefox/entrypoint.sh
+++ b/openvidu-server/docker/openvidu-recording/firefox/entrypoint.sh
@@ -30,38 +30,28 @@ mkdir /recordings/$VIDEO_ID
 chmod 777 /recordings/$VIDEO_ID
 echo $RECORDING_JSON > /recordings/$VIDEO_ID/.recording.$VIDEO_ID
 
-### Get a free display identificator ###
-
-DISPLAY_NUM=99
-DONE="no"
-
-while [ "$DONE" == "no" ]
-do
-  out=$(xdpyinfo -display :$DISPLAY_NUM 2>&1)
-  if [[ "$out" == name* ]] || [[ "$out" == Invalid* ]]
-  then
-     # Command succeeded; or failed with access error;  display exists
-     (( DISPLAY_NUM+=1 ))
-  else
-     # Display doesn't exist
-     DONE="yes"
-  fi
-done
-
-export DISPLAY_NUM
-
-echo "First available display -> :$DISPLAY_NUM"
-echo "----------------------------------------"
-
 pulseaudio -D
 
-### Start Chrome in headless mode with xvfb, using the display num previously obtained ###
+### Start Chrome in headless mode with xvfb, using an automatically provided free display num ###
 
 touch xvfb.log
 chmod 777 xvfb.log
-xvfb-run --server-num=${DISPLAY_NUM} --server-args="-ac -screen 0 ${RESOLUTION}x24 -noreset" firefox --width $WIDTH --height $HEIGHT $URL &> xvfb.log &
+xvfb-run --auto-servernum --server-args="-ac -screen 0 ${RESOLUTION}x24 -noreset" firefox --width $WIDTH --height $HEIGHT $URL &> xvfb.log &
 touch stop
 chmod 777 /recordings
+
+until pids=$(pidof Xvfb)
+do   
+    sleep 0.1
+done
+
+### Calculate the display num in use parsing args of command "Xvfb"
+
+XVFB_ARGS=$(ps -eo args | grep [X]vfb)
+DISPLAY_NUM=$(echo $XVFB_ARGS | sed 's/Xvfb :\([0-9]\+\).*/\1/')
+echo "Display in use -> :$DISPLAY_NUM"
+echo "----------------------------------------"
+
 sleep 5
 
 ### Start recording with ffmpeg ###