diff --git a/README.md b/README.md
index 4d922bb0..581db860 100644
--- a/README.md
+++ b/README.md
@@ -228,10 +228,6 @@ $ docker run -d \
 
 * The `com.github.jrcs.letsencrypt_nginx_proxy_companion.docker_gen` label - set this label on the docker-gen container to tell the docker-letsencrypt-nginx-proxy-companion container to use it as the docker-gen when it's split from nginx (separate containers).
 
-* `DOCKER_PROVIDER` - Set this to change behavior on container ID retrieval. Optional. Current supported values:
-  * No value (empty, not  set): no change in behavior.
-  * `ecs` [Amazon ECS using ECS_CONTAINER_METADATA_FILE environment variable](http://docs.aws.amazon.com/AmazonECS/latest/developerguide/container-metadata.html)
-
 * `DHPARAM_BITS` - Change the size of the Diffie-Hellman key generated by the container from the default value of 2048 bits. For example `-e DHPARAM_BITS=1024` to support some older clients like Java 6 and 7.
 
 #### Examples:
diff --git a/app/entrypoint.sh b/app/entrypoint.sh
index fd76c79f..3682957a 100755
--- a/app/entrypoint.sh
+++ b/app/entrypoint.sh
@@ -23,9 +23,11 @@ function check_docker_socket {
 
 function check_writable_directory {
     local dir="$1"
-    docker_api "/containers/${SELF_CID:-$(get_self_cid)}/json" | jq ".Mounts[].Destination" | grep -q "^\"$dir\"$"
-    if [[ $? -ne 0 ]]; then
-        echo "Warning: '$dir' does not appear to be a mounted volume."
+    if [[ $(get_self_cid) ]]; then
+        docker_api "/containers/$(get_self_cid)/json" | jq ".Mounts[].Destination" | grep -q "^\"$dir\"$"
+        [[ $? -ne 0 ]] && echo "Warning: '$dir' does not appear to be a mounted volume."
+    else
+        echo "Warning: can't check if '$dir' is a mounted volume without self container ID."
     fi
     if [[ ! -d "$dir" ]]; then
         echo "Error: can't access to '$dir' directory !" >&2
@@ -139,12 +141,6 @@ if [[ "$*" == "/bin/bash /app/start.sh" ]]; then
         exit 1
     fi
     check_docker_socket
-    if [[ -z "$(get_self_cid)" ]]; then
-        echo "Error: can't get my container ID !" >&2
-        exit 1
-    else
-        export SELF_CID="$(get_self_cid)"
-    fi
     if [[ -z "$(get_nginx_proxy_container)" ]]; then
         echo "Error: can't get nginx-proxy container ID !" >&2
         echo "Check that you are doing one of the following :" >&2
diff --git a/app/functions.sh b/app/functions.sh
index 0128540a..8d4957a6 100644
--- a/app/functions.sh
+++ b/app/functions.sh
@@ -60,22 +60,15 @@ function check_cert_min_validity {
 }
 
 function get_self_cid {
-    DOCKER_PROVIDER=${DOCKER_PROVIDER:-docker}
-
-    case "${DOCKER_PROVIDER}" in
-    ecs|ECS)
-        # AWS ECS. Enabled in /etc/ecs/ecs.config (http://docs.aws.amazon.com/AmazonECS/latest/developerguide/container-metadata.html)
-        if [[ -n "${ECS_CONTAINER_METADATA_FILE:-}" ]]; then
-            grep ContainerID "${ECS_CONTAINER_METADATA_FILE}" | sed 's/.*: "\(.*\)",/\1/g'
-        else
-            echo "${DOCKER_PROVIDER} specified as 'ecs' but not available. See: http://docs.aws.amazon.com/AmazonECS/latest/developerguide/container-metadata.html" >&2
-            exit 1
-        fi
-        ;;
-    *)
-        sed -nE 's/^.+docker[\/-]([a-f0-9]{64}).*/\1/p' /proc/self/cgroup | head -n 1
-        ;;
-    esac
+    local self_cid
+    self_cid="$(basename "$(cat /proc/1/cpuset)")"
+    if [[ -n "$self_cid" ]]; then
+        echo "$self_cid"
+        return 0
+    else
+        echo "$(date "+%Y/%m/%d %T"), Error: can't get my container ID !" >&2
+        return 1
+    fi
 }
 
 ## Docker API
@@ -162,8 +155,8 @@ function get_nginx_proxy_container {
         if [[ -n "${NGINX_PROXY_CONTAINER:-}" ]]; then
             nginx_cid="$NGINX_PROXY_CONTAINER"
         # ... else try to get the container ID with the volumes_from method.
-        else
-            volumes_from=$(docker_api "/containers/${SELF_CID:-$(get_self_cid)}/json" | jq -r '.HostConfig.VolumesFrom[]' 2>/dev/null)
+        elif [[ $(get_self_cid) ]]; then
+            volumes_from=$(docker_api "/containers/$(get_self_cid)/json" | jq -r '.HostConfig.VolumesFrom[]' 2>/dev/null)
             for cid in $volumes_from; do
                 cid="${cid%:*}" # Remove leading :ro or :rw set by remote docker-compose (thx anoopr)
                 if [[ $(docker_api "/containers/$cid/json" | jq -r '.Config.Env[]' | egrep -c '^NGINX_VERSION=') = "1" ]];then