diff --git a/README.md b/README.md
index 2476850..b25f5af 100644
--- a/README.md
+++ b/README.md
@@ -105,6 +105,9 @@ Enable IPv6 support. The network interface configuration is managed via systemd-
 ##### `ENABLE_SSHD`=true
 Install and enable OpenSSH service. The default configuration of the service doesn't allow `root` to login. Please use the user `pi` instead and `su -` or `sudo` to execute commands as root.
 
+##### `ENABLE_NONFREE`=false
+Allow the installation of non-free Debian packages that do not comply with the DFSG. This is required to install closed-source firmware binary blobs.
+
 ##### `ENABLE_RSYSLOG`=true
 If set to false, disable and uninstall rsyslog (so logs will be available only
 in journal files)
diff --git a/bootstrap.d/10-bootstrap.sh b/bootstrap.d/10-bootstrap.sh
index 2dfddff..771a3e4 100644
--- a/bootstrap.d/10-bootstrap.sh
+++ b/bootstrap.d/10-bootstrap.sh
@@ -5,13 +5,22 @@
 # Load utility functions
 . ./functions.sh
 
-# Base debootstrap (unpack only)
+VARIANT=""
+COMPONENTS="main"
+
+# Use non-free Debian packages if needed
+if [ "$ENABLE_NONFREE" = true ] ; then
+  COMPONENTS="main,non-free"
+fi
+
+# Use minbase bootstrap variant which only includes essential packages
 if [ "$ENABLE_MINBASE" = true ] ; then
-  http_proxy=${APT_PROXY} debootstrap --arch="${RELEASE_ARCH}" --foreign --variant=minbase --include="${APT_INCLUDES}" "${RELEASE}" "${R}" "http://${APT_SERVER}/debian"
-else
-  http_proxy=${APT_PROXY} debootstrap --arch="${RELEASE_ARCH}" --foreign --include="${APT_INCLUDES}" "${RELEASE}" "${R}" "http://${APT_SERVER}/debian"
+  VARIANT="--variant=minbase"
 fi
 
+# Base debootstrap (unpack only)
+http_proxy=${APT_PROXY} debootstrap --arch="${RELEASE_ARCH}" --foreign ${VARIANT} --components="${COMPONENTS}" --include="${APT_INCLUDES}" "${RELEASE}" "${R}" "http://${APT_SERVER}/debian"
+
 # Copy qemu emulator binary to chroot
 install_exec "${QEMU_BINARY}" "${R}${QEMU_BINARY}"
 
diff --git a/bootstrap.d/11-apt.sh b/bootstrap.d/11-apt.sh
index 991e7e1..cd2a51c 100644
--- a/bootstrap.d/11-apt.sh
+++ b/bootstrap.d/11-apt.sh
@@ -17,7 +17,7 @@ if [ "$BUILD_KERNEL" = false ] ; then
 
   # Install APT sources.list
   install_readonly files/apt/sources.list "${ETCDIR}/apt/sources.list"
-  echo "deb https://repositories.collabora.co.uk/debian ${RELEASE} rpi2" >> "${ETCDIR}/apt/sources.list"
+  echo "deb ${COLLABORA_URL} ${RELEASE} rpi2" >> "${ETCDIR}/apt/sources.list"
 
   # Upgrade collabora package index and install collabora keyring
   chroot_exec apt-get -qq -y update
@@ -31,6 +31,11 @@ else # BUILD_KERNEL=true
   sed -i "s/ jessie/ ${RELEASE}/" "${ETCDIR}/apt/sources.list"
 fi
 
+# Allow the installation of non-free Debian packages
+if [ "$ENABLE_NONFREE" = true ] ; then
+  sed -i "s/ contrib/ contrib non-free/" "${ETCDIR}/apt/sources.list"
+fi
+
 # Upgrade package index and update all installed packages and changed dependencies
 chroot_exec apt-get -qq -y update
 chroot_exec apt-get -qq -y -u dist-upgrade
diff --git a/bootstrap.d/13-kernel.sh b/bootstrap.d/13-kernel.sh
index c6b43c6..8e437c4 100644
--- a/bootstrap.d/13-kernel.sh
+++ b/bootstrap.d/13-kernel.sh
@@ -21,7 +21,7 @@ if [ "$BUILD_KERNEL" = true ] ; then
     fi
   else # KERNELSRC_DIR=""
     # Fetch current raspberrypi kernel sources
-    git -C "${R}/usr/src" clone --depth=1 https://github.com/raspberrypi/linux
+    git -C "${R}/usr/src" clone --depth=1 "${KERNEL_URL}"
   fi
 
   # Calculate optimal number of kernel building threads
@@ -142,13 +142,13 @@ if [ "$BUILD_KERNEL" = true ] ; then
     cp ${FIRMWAREDIR}/boot/start_x.elf ${BOOTDIR}/start_x.elf
   else
     # Install latest boot binaries from raspberry/firmware github
-    wget -q -O "${BOOTDIR}/bootcode.bin" https://github.com/raspberrypi/firmware/raw/master/boot/bootcode.bin
-    wget -q -O "${BOOTDIR}/fixup.dat" https://github.com/raspberrypi/firmware/raw/master/boot/fixup.dat
-    wget -q -O "${BOOTDIR}/fixup_cd.dat" https://github.com/raspberrypi/firmware/raw/master/boot/fixup_cd.dat
-    wget -q -O "${BOOTDIR}/fixup_x.dat" https://github.com/raspberrypi/firmware/raw/master/boot/fixup_x.dat
-    wget -q -O "${BOOTDIR}/start.elf" https://github.com/raspberrypi/firmware/raw/master/boot/start.elf
-    wget -q -O "${BOOTDIR}/start_cd.elf" https://github.com/raspberrypi/firmware/raw/master/boot/start_cd.elf
-    wget -q -O "${BOOTDIR}/start_x.elf" https://github.com/raspberrypi/firmware/raw/master/boot/start_x.elf
+    wget -q -O "${BOOTDIR}/bootcode.bin" "${FIRMWARE_URL}/bootcode.bin"
+    wget -q -O "${BOOTDIR}/fixup.dat" "${FIRMWARE_URL}/fixup.dat"
+    wget -q -O "${BOOTDIR}/fixup_cd.dat" "${FIRMWARE_URL}/fixup_cd.dat"
+    wget -q -O "${BOOTDIR}/fixup_x.dat" "${FIRMWARE_URL}/fixup_x.dat"
+    wget -q -O "${BOOTDIR}/start.elf" "${FIRMWARE_URL}/start.elf"
+    wget -q -O "${BOOTDIR}/start_cd.elf" "${FIRMWARE_URL}/start_cd.elf"
+    wget -q -O "${BOOTDIR}/start_x.elf" "${FIRMWARE_URL}/start_x.elf"
   fi
 
 else # BUILD_KERNEL=false
diff --git a/bootstrap.d/41-uboot.sh b/bootstrap.d/41-uboot.sh
index 19ad084..dca9cfc 100644
--- a/bootstrap.d/41-uboot.sh
+++ b/bootstrap.d/41-uboot.sh
@@ -13,7 +13,7 @@ fi
 # Fetch and build U-Boot bootloader
 if [ "$ENABLE_UBOOT" = true ] ; then
   # Fetch U-Boot bootloader sources
-  git -C "${R}/tmp" clone git://git.denx.de/u-boot.git
+  git -C "${R}/tmp" clone "${UBOOT_URL}"
 
   # Build and install U-Boot inside chroot
   chroot_exec make -C /tmp/u-boot/ ${UBOOT_CONFIG} all
diff --git a/bootstrap.d/42-fbturbo.sh b/bootstrap.d/42-fbturbo.sh
index 4e03f53..c3619f0 100644
--- a/bootstrap.d/42-fbturbo.sh
+++ b/bootstrap.d/42-fbturbo.sh
@@ -7,7 +7,7 @@
 
 if [ "$ENABLE_FBTURBO" = true ] ; then
   # Fetch fbturbo driver sources
-  git -C "${R}/tmp" clone https://github.com/ssvb/xf86-video-fbturbo.git
+  git -C "${R}/tmp" clone "${FBTURBO_URL}"
 
   # Install Xorg build dependencies
   chroot_exec apt-get -q -y --no-install-recommends install xorg-dev xutils-dev x11proto-dri2-dev libltdl-dev libtool automake libdrm-dev
diff --git a/rpi2-gen-image.sh b/rpi2-gen-image.sh
index f2d3d4d..2d17f12 100755
--- a/rpi2-gen-image.sh
+++ b/rpi2-gen-image.sh
@@ -47,6 +47,13 @@ DTB_FILE=${DTB_FILE:=bcm2709-rpi-2-b.dtb}
 UBOOT_CONFIG=${UBOOT_CONFIG:=rpi_2_defconfig}
 QEMU_BINARY=${QEMU_BINARY:=/usr/bin/qemu-arm-static}
 
+# URLs
+KERNEL_URL=${KERNEL_URL:=https://github.com/raspberrypi/linux}
+FIRMWARE_URL=${FIRMWARE_URL:=https://github.com/raspberrypi/firmware/raw/master/boot}
+COLLABORA_URL=${COLLABORA_URL:=https://repositories.collabora.co.uk/debian}
+FBTURBO_URL=${FBTURBO_URL:=https://github.com/ssvb/xf86-video-fbturbo.git}
+UBOOT_URL=${UBOOT_URL:=git://git.denx.de/u-boot.git}
+
 # Build directories
 BASEDIR="$(pwd)/images/${RELEASE}"
 BUILDDIR="${BASEDIR}/build"
@@ -93,6 +100,7 @@ APT_SERVER=${APT_SERVER:="ftp.debian.org"}
 ENABLE_CONSOLE=${ENABLE_CONSOLE:=true}
 ENABLE_IPV6=${ENABLE_IPV6:=true}
 ENABLE_SSHD=${ENABLE_SSHD:=true}
+ENABLE_NONFREE=${ENABLE_NONFREE:=false}
 ENABLE_SOUND=${ENABLE_SOUND:=true}
 ENABLE_DBUS=${ENABLE_DBUS:=true}
 ENABLE_HWRANDOM=${ENABLE_HWRANDOM:=true}