Cronjob added inside container

Dockerfile

@@ -1,4 +1,4 @@
-FROM ruby:2.7
+FROM ruby:3.1
 
 ENV BUILD_PACKAGES="apt-utils build-essential curl less nodejs sudo wget zsh libmariadb-dev libserialport-dev cron"
 
@@ -14,7 +14,18 @@ COPY Gemfile Gemfile.lock ./
 RUN \
   apt-get update -qq && \
   apt-get install -y $BUILD_PACKAGES && \
-  bundle install
+  # Fix bundler version BEFORE bundle install
+  gem install bundler -v "$(grep -A 1 'BUNDLED WITH' Gemfile.lock | tail -n 1)" && \
+  bundle install && \
+  rm -rf /var/lib/apt/lists/*
 
+# Copy cron file (if you use /etc/cron.d style)
+COPY reportcron /etc/cron.d/reportcron
+RUN chmod 0644 /etc/cron.d/reportcron && touch /var/log/cron.log
+
+# Add entrypoint script
+COPY docker-entrypoint.sh /usr/local/bin/docker-entrypoint.sh
+RUN chmod +x /usr/local/bin/docker-entrypoint.sh
+
+ENTRYPOINT ["/usr/local/bin/docker-entrypoint.sh"]
 
-CMD ["/bin/bash -c ruby ./smartmeter.rb"]