diff --git a/1.21/10-listen-on-ipv6-by-default.sh b/1.21/10-listen-on-ipv6-by-default.sh
new file mode 100644
index 0000000..b91e1e1
--- /dev/null
+++ b/1.21/10-listen-on-ipv6-by-default.sh
@@ -0,0 +1,61 @@
+#!/bin/sh
+# vim:sw=4:ts=4:et
+
+set -e
+
+ME=$(basename $0)
+DEFAULT_CONF_FILE="etc/nginx/conf.d/default.conf"
+
+# check if we have ipv6 available
+if [ ! -f "/proc/net/if_inet6" ]; then
+    echo >&3 "$ME: info: ipv6 not available"
+    exit 0
+fi
+
+if [ ! -f "/$DEFAULT_CONF_FILE" ]; then
+    echo >&3 "$ME: info: /$DEFAULT_CONF_FILE is not a file or does not exist"
+    exit 0
+fi
+
+# check if the file can be modified, e.g. not on a r/o filesystem
+touch /$DEFAULT_CONF_FILE 2>/dev/null || { echo >&3 "$ME: info: can not modify /$DEFAULT_CONF_FILE (read-only file system?)"; exit 0; }
+
+# check if the file is already modified, e.g. on a container restart
+grep -q "listen  \[::]\:8080;" /$DEFAULT_CONF_FILE && { echo >&3 "$ME: info: IPv6 listen already enabled"; exit 0; }
+
+if [ -f "/etc/os-release" ]; then
+    . /etc/os-release
+else
+    echo >&3 "$ME: info: can not guess the operating system"
+    exit 0
+fi
+
+echo >&3 "$ME: info: Getting the checksum of /$DEFAULT_CONF_FILE"
+
+case "$ID" in
+    "debian")
+        CHECKSUM=$(dpkg-query --show --showformat='${Conffiles}\n' nginx | grep $DEFAULT_CONF_FILE | cut -d' ' -f 3)
+        echo "$CHECKSUM  /$DEFAULT_CONF_FILE" | md5sum -c - >/dev/null 2>&1 || {
+            echo >&3 "$ME: info: /$DEFAULT_CONF_FILE differs from the packaged version"
+            exit 0
+        }
+        ;;
+    "alpine")
+        CHECKSUM=$(apk manifest nginx 2>/dev/null| grep $DEFAULT_CONF_FILE | cut -d' ' -f 1 | cut -d ':' -f 2)
+        echo "$CHECKSUM  /$DEFAULT_CONF_FILE" | sha1sum -c - >/dev/null 2>&1 || {
+            echo >&3 "$ME: info: /$DEFAULT_CONF_FILE differs from the packaged version"
+            exit 0
+        }
+        ;;
+    *)
+        echo >&3 "$ME: info: Unsupported distribution"
+        exit 0
+        ;;
+esac
+
+# enable ipv6 on default.conf listen sockets
+sed -i -E 's,listen       8080;,listen       8080;\n    listen  [::]:8080;,' /$DEFAULT_CONF_FILE
+
+echo >&3 "$ME: info: Enabled listen on IPv6 in /$DEFAULT_CONF_FILE"
+
+exit 0
diff --git a/1.21/20-envsubst-on-templates.sh b/1.21/20-envsubst-on-templates.sh
new file mode 100644
index 0000000..4f33029
--- /dev/null
+++ b/1.21/20-envsubst-on-templates.sh
@@ -0,0 +1,32 @@
+#!/bin/sh
+
+set -e
+
+ME=$(basename $0)
+
+auto_envsubst() {
+  local template_dir="${NGINX_ENVSUBST_TEMPLATE_DIR:-/etc/nginx/templates}"
+  local suffix="${NGINX_ENVSUBST_TEMPLATE_SUFFIX:-.template}"
+  local output_dir="${NGINX_ENVSUBST_OUTPUT_DIR:-/etc/nginx/conf.d}"
+
+  local template defined_envs relative_path output_path subdir
+  defined_envs=$(printf '${%s} ' $(env | cut -d= -f1))
+  [ -d "$template_dir" ] || return 0
+  if [ ! -w "$output_dir" ]; then
+    echo >&3 "$ME: ERROR: $template_dir exists, but $output_dir is not writable"
+    return 0
+  fi
+  find "$template_dir" -follow -type f -name "*$suffix" -print | while read -r template; do
+    relative_path="${template#$template_dir/}"
+    output_path="$output_dir/${relative_path%$suffix}"
+    subdir=$(dirname "$relative_path")
+    # create a subdirectory where the template file exists
+    mkdir -p "$output_dir/$subdir"
+    echo >&3 "$ME: Running envsubst on $template to $output_path"
+    envsubst "$defined_envs" < "$template" > "$output_path"
+  done
+}
+
+auto_envsubst
+
+exit 0
diff --git a/1.21/30-tune-worker-processes.sh b/1.21/30-tune-worker-processes.sh
new file mode 100644
index 0000000..5650587
--- /dev/null
+++ b/1.21/30-tune-worker-processes.sh
@@ -0,0 +1,188 @@
+#!/bin/sh
+# vim:sw=2:ts=2:sts=2:et
+
+set -eu
+
+LC_ALL=C
+ME=$( basename "$0" )
+PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
+
+[ "${NGINX_ENTRYPOINT_WORKER_PROCESSES_AUTOTUNE:-}" ] || exit 0
+
+touch /etc/nginx/nginx.conf 2>/dev/null || { echo >&2 "$ME: error: can not modify /etc/nginx/nginx.conf (read-only file system?)"; exit 0; }
+
+ceildiv() {
+  num=$1
+  div=$2
+  echo $(( (num + div - 1) / div ))
+}
+
+get_cpuset() {
+  cpusetroot=$1
+  cpusetfile=$2
+  ncpu=0
+  [ -f "$cpusetroot/$cpusetfile" ] || return 1
+  for token in $( tr ',' ' ' < "$cpusetroot/$cpusetfile" ); do
+    case "$token" in
+      *-*)
+        count=$( seq $(echo "$token" | tr '-' ' ') | wc -l )
+        ncpu=$(( ncpu+count ))
+        ;;
+      *)
+        ncpu=$(( ncpu+1 ))
+        ;;
+    esac
+  done
+  echo "$ncpu"
+}
+
+get_quota() {
+  cpuroot=$1
+  ncpu=0
+  [ -f "$cpuroot/cpu.cfs_quota_us" ] || return 1
+  [ -f "$cpuroot/cpu.cfs_period_us" ] || return 1
+  cfs_quota=$( cat "$cpuroot/cpu.cfs_quota_us" )
+  cfs_period=$( cat "$cpuroot/cpu.cfs_period_us" )
+  [ "$cfs_quota" = "-1" ] && return 1
+  [ "$cfs_period" = "0" ] && return 1
+  ncpu=$( ceildiv "$cfs_quota" "$cfs_period" )
+  [ "$ncpu" -gt 0 ] || return 1
+  echo "$ncpu"
+}
+
+get_quota_v2() {
+  cpuroot=$1
+  ncpu=0
+  [ -f "$cpuroot/cpu.max" ] || return 1
+  cfs_quota=$( cut -d' ' -f 1 < "$cpuroot/cpu.max" )
+  cfs_period=$( cut -d' ' -f 2 < "$cpuroot/cpu.max" )
+  [ "$cfs_quota" = "max" ] && return 1
+  [ "$cfs_period" = "0" ] && return 1
+  ncpu=$( ceildiv "$cfs_quota" "$cfs_period" )
+  [ "$ncpu" -gt 0 ] || return 1
+  echo "$ncpu"
+}
+
+get_cgroup_v1_path() {
+  needle=$1
+  found=
+  foundroot=
+  mountpoint=
+
+  [ -r "/proc/self/mountinfo" ] || return 1
+  [ -r "/proc/self/cgroup" ] || return 1
+
+  while IFS= read -r line; do
+    case "$needle" in
+      "cpuset")
+        case "$line" in
+          *cpuset*)
+            found=$( echo "$line" | cut -d ' ' -f 4,5 )
+            break
+            ;;
+        esac
+        ;;
+      "cpu")
+        case "$line" in
+          *cpuset*)
+            ;;
+          *cpu,cpuacct*|*cpuacct,cpu|*cpuacct*|*cpu*)
+            found=$( echo "$line" | cut -d ' ' -f 4,5 )
+            break
+            ;;
+        esac
+    esac
+  done << __EOF__
+$( grep -F -- '- cgroup ' /proc/self/mountinfo )
+__EOF__
+
+  while IFS= read -r line; do
+    controller=$( echo "$line" | cut -d: -f 2 )
+    case "$needle" in
+      "cpuset")
+        case "$controller" in
+          cpuset)
+            mountpoint=$( echo "$line" | cut -d: -f 3 )
+            break
+            ;;
+        esac
+        ;;
+      "cpu")
+        case "$controller" in
+          cpu,cpuacct|cpuacct,cpu|cpuacct|cpu)
+            mountpoint=$( echo "$line" | cut -d: -f 3 )
+            break
+            ;;
+        esac
+        ;;
+    esac
+done << __EOF__
+$( grep -F -- 'cpu' /proc/self/cgroup )
+__EOF__
+
+  case "${found%% *}" in
+    "/")
+      foundroot="${found##* }$mountpoint"
+      ;;
+    "$mountpoint")
+      foundroot="${found##* }"
+      ;;
+  esac
+  echo "$foundroot"
+}
+
+get_cgroup_v2_path() {
+  found=
+  foundroot=
+  mountpoint=
+
+  [ -r "/proc/self/mountinfo" ] || return 1
+  [ -r "/proc/self/cgroup" ] || return 1
+
+  while IFS= read -r line; do
+    found=$( echo "$line" | cut -d ' ' -f 4,5 )
+  done << __EOF__
+$( grep -F -- '- cgroup2 ' /proc/self/mountinfo )
+__EOF__
+
+  while IFS= read -r line; do
+    mountpoint=$( echo "$line" | cut -d: -f 3 )
+done << __EOF__
+$( grep -F -- '0::' /proc/self/cgroup )
+__EOF__
+
+  case "${found%% *}" in
+    "")
+      return 1
+      ;;
+    "/")
+      foundroot="${found##* }$mountpoint"
+      ;;
+    "$mountpoint")
+      foundroot="${found##* }"
+      ;;
+  esac
+  echo "$foundroot"
+}
+
+ncpu_online=$( getconf _NPROCESSORS_ONLN )
+ncpu_cpuset=
+ncpu_quota=
+ncpu_cpuset_v2=
+ncpu_quota_v2=
+
+cpuset=$( get_cgroup_v1_path "cpuset" ) && ncpu_cpuset=$( get_cpuset "$cpuset" "cpuset.effective_cpus" ) || ncpu_cpuset=$ncpu_online
+cpu=$( get_cgroup_v1_path "cpu" ) && ncpu_quota=$( get_quota "$cpu" ) || ncpu_quota=$ncpu_online
+cgroup_v2=$( get_cgroup_v2_path ) && ncpu_cpuset_v2=$( get_cpuset "$cgroup_v2" "cpuset.cpus.effective" ) || ncpu_cpuset_v2=$ncpu_online
+cgroup_v2=$( get_cgroup_v2_path ) && ncpu_quota_v2=$( get_quota_v2 "$cgroup_v2" ) || ncpu_quota_v2=$ncpu_online
+
+ncpu=$( printf "%s\n%s\n%s\n%s\n%s\n" \
+               "$ncpu_online" \
+               "$ncpu_cpuset" \
+               "$ncpu_quota" \
+               "$ncpu_cpuset_v2" \
+               "$ncpu_quota_v2" \
+               | sort -n \
+               | head -n 1 )
+
+sed -i.bak -r 's/^(worker_processes)(.*)$/# Commented out by '"$ME"' on '"$(date)"'\n#\1\2\n\1 '"$ncpu"';/' /etc/nginx/nginx.conf
diff --git a/1.21/Dockerfile b/1.21/Dockerfile
new file mode 100644
index 0000000..9f558db
--- /dev/null
+++ b/1.21/Dockerfile
@@ -0,0 +1,151 @@
+FROM harbor.dragse.it/base/alpine:3.15
+
+LABEL maintainer="Lennard Brinkhaus <lennard.brinkhaus@dragse.de>"
+
+ENV NGINX_VERSION 1.21.5
+ENV NJS_VERSION   0.7.1
+ENV PKG_RELEASE   1
+
+RUN echo $'http://nexus.dragse.it/repository/apk-main/\nhttp://nexus.dragse.it/repository/apk-community/' > /etc/apk/repositories
+
+RUN   apk --no-cache upgrade \
+  &&   apk --no-cache add ca-certificates wget openssl \
+  &&   update-ca-certificates
+
+ARG UID=101
+ARG GID=101
+
+RUN set -x \
+# create nginx user/group first, to be consistent throughout docker variants
+    && addgroup -g $GID -S nginx || true \
+    && adduser -S -D -H -u $UID -h /var/cache/nginx -s /sbin/nologin -G nginx -g nginx nginx || true \
+    && apkArch="$(cat /etc/apk/arch)" \
+    && nginxPackages=" \
+        nginx=${NGINX_VERSION}-r${PKG_RELEASE} \
+        nginx-module-xslt=${NGINX_VERSION}-r${PKG_RELEASE} \
+        nginx-module-geoip=${NGINX_VERSION}-r${PKG_RELEASE} \
+        nginx-module-image-filter=${NGINX_VERSION}-r${PKG_RELEASE} \
+        nginx-module-perl=${NGINX_VERSION}-r${PKG_RELEASE} \
+        nginx-module-njs=${NGINX_VERSION}.${NJS_VERSION}-r${PKG_RELEASE} \
+    " \
+# install prerequisites for public key and pkg-oss checks
+    && apk add --no-cache --virtual .checksum-deps \
+        openssl \
+    && case "$apkArch" in \
+        x86_64|aarch64) \
+# arches officially built by upstream
+            set -x \
+            && KEY_SHA512="e7fa8303923d9b95db37a77ad46c68fd4755ff935d0a534d26eba83de193c76166c68bfe7f65471bf8881004ef4aa6df3e34689c305662750c0172fca5d8552a *stdin" \
+            && wget -O /tmp/nginx_signing.rsa.pub https://nginx.org/keys/nginx_signing.rsa.pub \
+            && if [ "$(openssl rsa -pubin -in /tmp/nginx_signing.rsa.pub -text -noout | openssl sha512 -r)" = "$KEY_SHA512" ]; then \
+                echo "key verification succeeded!"; \
+                mv /tmp/nginx_signing.rsa.pub /etc/apk/keys/; \
+            else \
+                echo "key verification failed!"; \
+                exit 1; \
+            fi \
+            && apk add -X "https://nginx.org/packages/mainline/alpine/v$(egrep -o '^[0-9]+\.[0-9]+' /etc/alpine-release)/main" --no-cache $nginxPackages \
+            ;; \
+        *) \
+# we're on an architecture upstream doesn't officially build for
+# let's build binaries from the published packaging sources
+            set -x \
+            && tempDir="$(mktemp -d)" \
+            && chown nobody:nobody $tempDir \
+            && apk add --no-cache --virtual .build-deps \
+                gcc \
+                libc-dev \
+                make \
+                openssl-dev \
+                pcre-dev \
+                zlib-dev \
+                linux-headers \
+                libxslt-dev \
+                gd-dev \
+                geoip-dev \
+                perl-dev \
+                libedit-dev \
+                bash \
+                alpine-sdk \
+                findutils \
+            && su nobody -s /bin/sh -c " \
+                export HOME=${tempDir} \
+                && cd ${tempDir} \
+                && curl -f -O https://hg.nginx.org/pkg-oss/archive/${NGINX_VERSION}-${PKG_RELEASE}.tar.gz \
+                && PKGOSSCHECKSUM=\"f917c27702aa89cda46878fc80d446839c592c43ce7f251b3f4ced60c7033d34496a92d283927225d458cbc4f2f89499e7fb16344923317cd7725ad722eaf93e *${NGINX_VERSION}-${PKG_RELEASE}.tar.gz\" \
+                && if [ \"\$(openssl sha512 -r ${NGINX_VERSION}-${PKG_RELEASE}.tar.gz)\" = \"\$PKGOSSCHECKSUM\" ]; then \
+                    echo \"pkg-oss tarball checksum verification succeeded!\"; \
+                else \
+                    echo \"pkg-oss tarball checksum verification failed!\"; \
+                    exit 1; \
+                fi \
+                && tar xzvf ${NGINX_VERSION}-${PKG_RELEASE}.tar.gz \
+                && cd pkg-oss-${NGINX_VERSION}-${PKG_RELEASE} \
+                && cd alpine \
+                && make all \
+                && apk index -o ${tempDir}/packages/alpine/${apkArch}/APKINDEX.tar.gz ${tempDir}/packages/alpine/${apkArch}/*.apk \
+                && abuild-sign -k ${tempDir}/.abuild/abuild-key.rsa ${tempDir}/packages/alpine/${apkArch}/APKINDEX.tar.gz \
+                " \
+            && cp ${tempDir}/.abuild/abuild-key.rsa.pub /etc/apk/keys/ \
+            && apk del .build-deps \
+            && apk add -X ${tempDir}/packages/alpine/ --no-cache $nginxPackages \
+            ;; \
+    esac \
+# remove checksum deps
+    && apk del .checksum-deps \
+# if we have leftovers from building, let's purge them (including extra, unnecessary build deps)
+    && if [ -n "$tempDir" ]; then rm -rf "$tempDir"; fi \
+    && if [ -n "/etc/apk/keys/abuild-key.rsa.pub" ]; then rm -f /etc/apk/keys/abuild-key.rsa.pub; fi \
+    && if [ -n "/etc/apk/keys/nginx_signing.rsa.pub" ]; then rm -f /etc/apk/keys/nginx_signing.rsa.pub; fi \
+# Bring in gettext so we can get `envsubst`, then throw
+# the rest away. To do this, we need to install `gettext`
+# then move `envsubst` out of the way so `gettext` can
+# be deleted completely, then move `envsubst` back.
+    && apk add --no-cache --virtual .gettext gettext \
+    && mv /usr/bin/envsubst /tmp/ \
+    \
+    && runDeps="$( \
+        scanelf --needed --nobanner /tmp/envsubst \
+            | awk '{ gsub(/,/, "\nso:", $2); print "so:" $2 }' \
+            | sort -u \
+            | xargs -r apk info --installed \
+            | sort -u \
+    )" \
+    && apk add --no-cache $runDeps \
+    && apk del .gettext \
+    && mv /tmp/envsubst /usr/local/bin/ \
+# Bring in tzdata so users could set the timezones through the environment
+# variables
+    && apk add --no-cache tzdata \
+# Bring in curl and ca-certificates to make registering on DNS SD easier
+    && apk add --no-cache curl ca-certificates \
+# forward request and error logs to docker log collector
+    && ln -sf /dev/stdout /var/log/nginx/access.log \
+    && ln -sf /dev/stderr /var/log/nginx/error.log \
+# create a docker-entrypoint.d directory
+    && mkdir /docker-entrypoint.d
+
+# implement changes required to run NGINX as an unprivileged user
+RUN sed -i 's,listen       80;,listen       8080;,' /etc/nginx/conf.d/default.conf \
+    && sed -i '/user  nginx;/d' /etc/nginx/nginx.conf \
+    && sed -i 's,/var/run/nginx.pid,/tmp/nginx.pid,' /etc/nginx/nginx.conf \
+    && sed -i "/^http {/a \    proxy_temp_path /tmp/proxy_temp;\n    client_body_temp_path /tmp/client_temp;\n    fastcgi_temp_path /tmp/fastcgi_temp;\n    uwsgi_temp_path /tmp/uwsgi_temp;\n    scgi_temp_path /tmp/scgi_temp;\n" /etc/nginx/nginx.conf \
+# nginx user must own the cache and etc directory to write cache and tweak the nginx config
+    && chown -R $UID:0 /var/cache/nginx \
+    && chmod -R g+w /var/cache/nginx \
+    && chown -R $UID:0 /etc/nginx \
+    && chmod -R g+w /etc/nginx
+
+COPY docker-entrypoint.sh /
+COPY 10-listen-on-ipv6-by-default.sh /docker-entrypoint.d
+COPY 20-envsubst-on-templates.sh /docker-entrypoint.d
+COPY 30-tune-worker-processes.sh /docker-entrypoint.d
+ENTRYPOINT ["/docker-entrypoint.sh"]
+
+EXPOSE 8080
+
+STOPSIGNAL SIGQUIT
+
+USER $UID
+
+CMD ["nginx", "-g", "daemon off;"]
diff --git a/1.21/docker-entrypoint.sh b/1.21/docker-entrypoint.sh
new file mode 100644
index 0000000..72d5cd9
--- /dev/null
+++ b/1.21/docker-entrypoint.sh
@@ -0,0 +1,38 @@
+#!/bin/sh
+# vim:sw=4:ts=4:et
+
+set -e
+
+if [ -z "${NGINX_ENTRYPOINT_QUIET_LOGS:-}" ]; then
+    exec 3>&1
+else
+    exec 3>/dev/null
+fi
+
+if [ "$1" = "nginx" -o "$1" = "nginx-debug" ]; then
+    if /usr/bin/find "/docker-entrypoint.d/" -mindepth 1 -maxdepth 1 -type f -print -quit 2>/dev/null | read v; then
+        echo >&3 "$0: /docker-entrypoint.d/ is not empty, will attempt to perform configuration"
+
+        echo >&3 "$0: Looking for shell scripts in /docker-entrypoint.d/"
+        find "/docker-entrypoint.d/" -follow -type f -print | sort -V | while read -r f; do
+            case "$f" in
+                *.sh)
+                    if [ -x "$f" ]; then
+                        echo >&3 "$0: Launching $f";
+                        "$f"
+                    else
+                        # warn on shell scripts without exec bit
+                        echo >&3 "$0: Ignoring $f, not executable";
+                    fi
+                    ;;
+                *) echo >&3 "$0: Ignoring $f";;
+            esac
+        done
+
+        echo >&3 "$0: Configuration complete; ready for start up"
+    else
+        echo >&3 "$0: No files found in /docker-entrypoint.d/, skipping configuration"
+    fi
+fi
+
+exec "$@"