+# first add xenial repo needed for installing qemu_static_user/xenial in the container
+# then add complementary architecture repositories in case the cloud image is of different arch
+echo -e "deb [arch="${DOCKER_ARCH}"] "${DOCKER_REPO}" xenial-updates universe
+deb [arch="${EXTRA_ARCH}"] "${EXTRA_REPO}" trusty main universe multiverse restricted
+deb [arch="${EXTRA_ARCH}"] "${EXTRA_REPO}" trusty-updates main universe multiverse restricted
+deb [arch="${EXTRA_ARCH}"] "${EXTRA_REPO}" trusty-security main universe multiverse restricted
+deb [arch="${EXTRA_ARCH}"] "${EXTRA_REPO}" trusty-proposed main universe multiverse restricted" > "${sub_source_file}"
+
+echo "vm.mmap_min_addr = 0" > /etc/sysctl.d/mmap_min_addr.conf