multi arch S6 with fixed S6 version

Dockerfile

@@ -10,12 +10,34 @@ FROM node:alpine as app
 ENV NODE_ENV production
 ADD root/ /
 
-# add S6 Overlay
-ADD https://github.com/just-containers/s6-overlay/releases/latest/download/s6-overlay-noarch.tar.xz /tmp
-ADD https://github.com/just-containers/s6-overlay/releases/latest/download/s6-overlay-x86_64.tar.xz /tmp
-RUN tar -C / -Jxpf /tmp/s6-overlay-noarch.tar.xz \
- && tar -C / -Jxpf /tmp/s6-overlay-x86_64.tar.xz \
- && apk add --no-cache shadow tzdata # install shadow (for groupmod and usermod) and tzdata (for TZ env variable)
+# sets version for s6 overlay
+ARG S6_SRC_DEP="ca-certificates xz-utils wget"
+ARG S6_SRC_URL="https://github.com/just-containers/s6-overlay/releases/download"
+ARG S6_VERSION=v3.1.1.2
+
+# detect system arch then select the right version of s6
+RUN export SYS_ARCH=$(uname -m); \
+    case "$SYS_ARCH" in \
+        aarch64 ) export S6_ARCH='aarch64' ;; \
+        arm64   ) export S6_ARCH='aarch64' ;; \
+        armhf   ) export S6_ARCH='armhf'   ;; \
+        arm*    ) export S6_ARCH='arm'     ;; \
+        i4*     ) export S6_ARCH='i486'    ;; \
+        i6*     ) export S6_ARCH='i686'    ;; \
+        riscv64 ) export S6_ARCH='riscv64' ;; \
+        s390*   ) export S6_ARCH='s390x'   ;; \
+        *       ) export S6_ARCH='x86_64'  ;; \
+    esac; \
+    untar (){ \
+        echo "⏬ Downloading $1"; \
+        wget -O- $1 | tar Jxp -C /; \
+    }; \
+    \
+    echo "⬇️ Downloading s6 overlay:${S6_ARCH}-${S6_VERSION} for ${SYS_ARCH}" \
+        && untar ${S6_SRC_URL}/${S6_VERSION}/s6-overlay-noarch.tar.xz \
+        && untar ${S6_SRC_URL}/${S6_VERSION}/s6-overlay-${S6_ARCH}.tar.xz \
+    echo "⬇️ Install shadow (for groupmod and usermod) and tzdata (for TZ env variable)" \
+    && apk add --no-cache shadow tzdata
 
 # add builded app
 WORKDIR /app