I am having a nasty time running a non-root crontab file on Alpine Linux.
I've been through two other cron related posts and I don't have an answer:
https://askubuntu.com/questions/23009/why-crontab-scripts-are-not-working
https://serverfault.com/questions/449651/why-is-my-crontab-not-working-and-how-can-i-troubleshoot-it
Here is the setup.
My crontab looks like this:
PATH=/usr/local/bin:/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/sbin:/opt/aws/bin:/home/ec2-user/bin
SHELL=/bin/bash
* * * * * /opt/monitor/monitor.sh >> /var/log/monitor.log 2>&1
0 3 * * * /opt/monitor/monitor-log-clean.sh >> /var/log/monitor.log 2>&1
My Dockerfile is a little messy now, but only because I have been desperately trying to resolve this. It looks something like this. In short, I add SUID for crontab -e to work as other users, I create my user, I import my crontab file, and then I provide permissions to everything I can think of.
FROM alpine:3.5
# DEPENDENCY TO ALLOW USERS TO RUN crontab -e
RUN apk add --update busybox-suid
# I LIKE BASH
RUN apk --no-cache add bash bash-doc
RUN apk --no-cache add util-linux pciutils usbutils coreutils binutils findutils grep
#... lots of custom stuff ...
# CREATE USER
RUN adduser -S robuser && \
mkdir -p /home/robuser
# ADD ENTRY POINT
ADD src/entrypoint.sh /home/robuser/entrypoint.sh
# GIVE MY USER ACCESS
RUN mkdir /etc/cron.d
RUN echo "robuser" > /etc/cron.allow
RUN echo "" >> /etc/cron.allow
RUN chmod -R 644 /etc/cron.d
# ADD MY CRONTAB
RUN mkdir -p /var/spool/cron/crontabs
ADD ./src/crontab.conf /tmp/cloudwatch/crontab.conf
RUN crontab -u robuser /tmp/cloudwatch/crontab.conf
# DEBUG... GIVE MY USER ACCESS TO EVERYTHING
RUN chown -R robuser /etc/cron.d
RUN chmod -R 755 /etc/cron.d
RUN chown -R robuser /var/spool/cron
RUN chmod -R 744 /var/spool/cron
RUN chown robuser /var/spool/cron/crontabs
RUN chmod 744 /var/spool/cron/crontabs
RUN chown -R robuser /etc/crontabs
RUN chmod -R 744 /etc/crontabs
RUN chown robuser /etc/crontabs/robuser
RUN chmod -R 744 /etc/crontabs/robuser
RUN chmod 600 /var/spool/cron/crontabs/robuser
# ADD MY MONITORING PROGRAM
RUN mkdir -p /opt/monitor
ADD src/monitor /opt/monitor
RUN mkdir -p /opt/monitor/.tmp && \
chown -R robuser /opt/monitor && \
chmod -R 700 /opt/monitor
RUN touch /var/log/entrypoint.log && \
touch /var/log/monitor.log && \
touch /var/log/cron.log && \
touch /var/log/awslogs.log && \
chown -R robuser /var/log
USER robuser
ENTRYPOINT /home/robuser/entrypoint.sh
meanwhile, my entrypoint.sh has this somewhere in it. I start the cron daemon as a background service and log to cron.log verbosely. I've also tried specifying -d 0 to get even more debug, but the didn't really add anything to the output.
#!/bin/bash
crond -b -l 0 -L /var/log/cron.log
#... lots of other startup stuff ...
An important point: If I don't switch to robuser, everything works okay as root.
If I check the cron.log, its pretty empty:
crond: crond (busybox 1.25.1) started, log level 0
crond: wakeup dt=45
crond: wakeup dt=60
crond: wakeup dt=60
Meanwhile, /var/log/monitor.log is completely empty (see crontab at the beginning of the post).
So crond is not printing any errors.
I've tried everything i can think of to debug this. There's no error message. It simply runs and never prints. A good suggestion was to simply my crontab.. but this also did not work:
PATH=/usr/local/bin:/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/sbin:/opt/aws/bin:/home/ec2-user/bin
SHELL=/bin/bash
* * * * * touch /tmp/test.txt
I've tried searching for other alpine containers who use non-root cron, but most people don't go through the trouble of getting their alpine containers to run non-root.
Does anyone have any further suggestions to help debug this?