#
# crond Dockerfile
#

# Pull base image.
FROM debian:jessie

# Install Nginx.
RUN DEBIAN_FRONTEND=noninteractive  \
  apt-get update && \
  apt-get install -y --no-install-recommends cron

# we need to make sure that /etc/cron.* cronjobs are not run as root
# it's not required for the operation (after all, all the cronjobs are to be
# doing is either some http requests, or some stuff against a database)
#
# first, remove the unnecessary cron.daily scripts
# 
# then, change the user to nobody for cron.(hourly|daily|weekly|monthly),
# conveniently configured in /etc/crontab
#
# finally, make sure that this sed script runs every few minutes on all /etc/cron.d files
RUN rm -rf /etc/cron.*/* \
 && sed -i -r -e 's/^(([/0-9*,-]+\s+){5}|@(reboot|yearly|annually|monthly|weekly|daily|midnight|hourly)\s+)root\s+(.*)/\1\tnobody\t\4/' /etc/crontab \
 && echo "*/15 * * * *  root  sed -i -r -e 's/^(([/0-9*,-]+\s+){5}|@(reboot|yearly|annually|monthly|weekly|daily|midnight|hourly)\s+)root\s+(.*)/\1\tnobody\t\4/' /etc/cron.d/*" >> /etc/crontab

# cron volumes
VOLUME ["/etc/cron.d", "/etc/cron.daily", "/etc/cron.hourly", "/etc/cron.monthly", "/etc/cron.weekly"]

# well
WORKDIR /etc

# command and entrypoint
CMD []
ENTRYPOINT ["/usr/sbin/cron", "-f"]