diff --git a/.examples/dockerfiles/full/apache/Dockerfile b/.examples/dockerfiles/full/apache/Dockerfile
index 178ca84..fe82de2 100644
--- a/.examples/dockerfiles/full/apache/Dockerfile
+++ b/.examples/dockerfiles/full/apache/Dockerfile
@@ -1,23 +1,58 @@
 FROM nextcloud:apache
 
-RUN mkdir -p /usr/share/man/man1 \
-    && apt-get update && apt-get install -y \
-        supervisor \
+RUN set -ex; \
+    \
+    apt-get update; \
+    apt-get install -y --no-install-recommends \
         ffmpeg \
-        libbz2-dev \
-        libgmp3-dev \
-        libc-client-dev \
-        libkrb5-dev \
         smbclient \
-        libsmbclient-dev \
+        supervisor \
 #       libreoffice \
-    && rm -rf /var/lib/apt/lists/* \
-    && docker-php-ext-configure imap --with-kerberos --with-imap-ssl \
-    && ln -s "/usr/include/$(dpkg-architecture --query DEB_BUILD_MULTIARCH)/gmp.h" /usr/include/gmp.h \
-    && docker-php-ext-install bz2 gmp imap \
-    && pecl install smbclient \
-    && docker-php-ext-enable smbclient \
-    && mkdir /var/log/supervisord /var/run/supervisord
+    ; \
+    rm -rf /var/lib/apt/lists/*
+
+RUN set -ex; \
+    \
+    savedAptMark="$(apt-mark showmanual)"; \
+    \
+    apt-get update; \
+    apt-get install -y --no-install-recommends \
+        libbz2-dev \
+        libc-client-dev \
+        libgmp3-dev \
+        libkrb5-dev \
+        libsmbclient-dev \
+    ; \
+    \
+    docker-php-ext-configure imap --with-kerberos --with-imap-ssl; \
+    ln -s "/usr/include/$(dpkg-architecture --query DEB_BUILD_MULTIARCH)/gmp.h" /usr/include/gmp.h; \
+    docker-php-ext-install \
+        bz2 \
+        gmp \
+        imap \
+    ; \
+    pecl install smbclient; \
+    docker-php-ext-enable smbclient; \
+    \
+# reset apt-mark's "manual" list so that "purge --auto-remove" will remove all build dependencies
+    apt-mark auto '.*' > /dev/null; \
+    apt-mark manual $savedAptMark; \
+    ldd "$(php -r 'echo ini_get("extension_dir");')"/*.so \
+        | awk '/=>/ { print $3 }' \
+        | sort -u \
+        | xargs -r dpkg-query -S \
+        | cut -d: -f1 \
+        | sort -u \
+        | xargs -rt apt-mark manual; \
+    \
+    apt-get purge -y --auto-remove -o APT::AutoRemove::RecommendsImportant=false; \
+    rm -rf /var/lib/apt/lists/*
+
+RUN mkdir -p \
+    /usr/share/man/man1 \
+    /var/log/supervisord \
+    /var/run/supervisord \
+;
 
 COPY supervisord.conf /etc/supervisor/supervisord.conf
 
diff --git a/.examples/dockerfiles/full/fpm/Dockerfile b/.examples/dockerfiles/full/fpm/Dockerfile
index b0c61d6..3e53e59 100644
--- a/.examples/dockerfiles/full/fpm/Dockerfile
+++ b/.examples/dockerfiles/full/fpm/Dockerfile
@@ -1,23 +1,58 @@
 FROM nextcloud:fpm
 
-RUN mkdir -p /usr/share/man/man1 \
-    && apt-get update && apt-get install -y \
-        supervisor \
+RUN set -ex; \
+    \
+    apt-get update; \
+    apt-get install -y --no-install-recommends \
         ffmpeg \
-        libbz2-dev \
-        libgmp3-dev \
-        libc-client-dev \
-        libkrb5-dev \
         smbclient \
-        libsmbclient-dev \
+        supervisor \
 #       libreoffice \
-    && rm -rf /var/lib/apt/lists/* \
-    && docker-php-ext-configure imap --with-kerberos --with-imap-ssl \
-    && ln -s "/usr/include/$(dpkg-architecture --query DEB_BUILD_MULTIARCH)/gmp.h" /usr/include/gmp.h \
-    && docker-php-ext-install bz2 gmp imap \
-    && pecl install smbclient \
-    && docker-php-ext-enable smbclient \
-    && mkdir /var/log/supervisord /var/run/supervisord
+    ; \
+    rm -rf /var/lib/apt/lists/*
+
+RUN set -ex; \
+    \
+    savedAptMark="$(apt-mark showmanual)"; \
+    \
+    apt-get update; \
+    apt-get install -y --no-install-recommends \
+        libbz2-dev \
+        libc-client-dev \
+        libgmp3-dev \
+        libkrb5-dev \
+        libsmbclient-dev \
+    ; \
+    \
+    docker-php-ext-configure imap --with-kerberos --with-imap-ssl; \
+    ln -s "/usr/include/$(dpkg-architecture --query DEB_BUILD_MULTIARCH)/gmp.h" /usr/include/gmp.h; \
+    docker-php-ext-install \
+        bz2 \
+        gmp \
+        imap \
+    ; \
+    pecl install smbclient; \
+    docker-php-ext-enable smbclient; \
+    \
+# reset apt-mark's "manual" list so that "purge --auto-remove" will remove all build dependencies
+    apt-mark auto '.*' > /dev/null; \
+    apt-mark manual $savedAptMark; \
+    ldd "$(php -r 'echo ini_get("extension_dir");')"/*.so \
+        | awk '/=>/ { print $3 }' \
+        | sort -u \
+        | xargs -r dpkg-query -S \
+        | cut -d: -f1 \
+        | sort -u \
+        | xargs -rt apt-mark manual; \
+    \
+    apt-get purge -y --auto-remove -o APT::AutoRemove::RecommendsImportant=false; \
+    rm -rf /var/lib/apt/lists/*
+
+RUN mkdir -p \
+    /usr/share/man/man1 \
+    /var/log/supervisord \
+    /var/run/supervisord \
+;
 
 COPY supervisord.conf /etc/supervisor/supervisord.conf
 
diff --git a/.examples/dockerfiles/imap/apache/Dockerfile b/.examples/dockerfiles/imap/apache/Dockerfile
index f7958c0..5f24c75 100644
--- a/.examples/dockerfiles/imap/apache/Dockerfile
+++ b/.examples/dockerfiles/imap/apache/Dockerfile
@@ -1,7 +1,28 @@
 FROM nextcloud:apache
 
-RUN apt-get update \
- && apt-get install -y libc-client-dev libkrb5-dev \
- && rm -rf /var/lib/apt/lists/* \
- && docker-php-ext-configure imap --with-kerberos --with-imap-ssl \
- && docker-php-ext-install imap
+RUN set -ex; \
+    \
+    savedAptMark="$(apt-mark showmanual)"; \
+    \
+    apt-get update; \
+    apt-get install -y --no-install-recommends \
+        libc-client-dev \
+        libkrb5-dev \
+    ; \
+    \
+    docker-php-ext-configure imap --with-kerberos --with-imap-ssl; \
+    docker-php-ext-install imap; \
+    \
+# reset apt-mark's "manual" list so that "purge --auto-remove" will remove all build dependencies
+    apt-mark auto '.*' > /dev/null; \
+    apt-mark manual $savedAptMark; \
+    ldd "$(php -r 'echo ini_get("extension_dir");')"/*.so \
+        | awk '/=>/ { print $3 }' \
+        | sort -u \
+        | xargs -r dpkg-query -S \
+        | cut -d: -f1 \
+        | sort -u \
+        | xargs -rt apt-mark manual; \
+    \
+    apt-get purge -y --auto-remove -o APT::AutoRemove::RecommendsImportant=false; \
+    rm -rf /var/lib/apt/lists/*
diff --git a/.examples/dockerfiles/imap/fpm/Dockerfile b/.examples/dockerfiles/imap/fpm/Dockerfile
index b403de6..f692fd7 100644
--- a/.examples/dockerfiles/imap/fpm/Dockerfile
+++ b/.examples/dockerfiles/imap/fpm/Dockerfile
@@ -1,7 +1,28 @@
 FROM nextcloud:fpm
 
-RUN apt-get update \
- && apt-get install -y libc-client-dev libkrb5-dev \
- && rm -rf /var/lib/apt/lists/* \
- && docker-php-ext-configure imap --with-kerberos --with-imap-ssl \
- && docker-php-ext-install imap
+RUN set -ex; \
+    \
+    savedAptMark="$(apt-mark showmanual)"; \
+    \
+    apt-get update; \
+    apt-get install -y --no-install-recommends \
+        libc-client-dev \
+        libkrb5-dev \
+    ; \
+    \
+    docker-php-ext-configure imap --with-kerberos --with-imap-ssl; \
+    docker-php-ext-install imap; \
+    \
+# reset apt-mark's "manual" list so that "purge --auto-remove" will remove all build dependencies
+    apt-mark auto '.*' > /dev/null; \
+    apt-mark manual $savedAptMark; \
+    ldd "$(php -r 'echo ini_get("extension_dir");')"/*.so \
+        | awk '/=>/ { print $3 }' \
+        | sort -u \
+        | xargs -r dpkg-query -S \
+        | cut -d: -f1 \
+        | sort -u \
+        | xargs -rt apt-mark manual; \
+    \
+    apt-get purge -y --auto-remove -o APT::AutoRemove::RecommendsImportant=false; \
+    rm -rf /var/lib/apt/lists/*