Run Cron Job inside Docker Container

hello.cronjob

To run a cron job inside a Docker container, you need to specify your cron job first inside a file.

* * * * * echo "Hello world" `date` >> /var/log/cron.log 2>&1

This cron job will echo-ing string and system date to a file. Please notice there is a new line in the end of file.

Dockerfile

Create a Dockerfile to run our cronjob using cron tab.

FROM ubuntu:14.04.1
MAINTAINER Edward Samuel Pasaribu <edwardsamuel92@gmail.com>

# Copy cron job to container
ADD hello.cronjob /opt/hello/hello.cronjob

# Change permission cron job file and load it with crontab
RUN \
    chmod 0644 /opt/hello/hello.cronjob && \
    crontab /opt/hello/hello.cronjob

# Create a file needed by hello.cronjob
RUN \
    touch /var/log/cron.log

# Run the command on container startup:
# - Run non-daemonized cron in background
# - Output the log result from hello.cronjob
CMD (cron -f &) && tail -f /var/log/cron.log

How to run

git clone https://github.com/edwardsamuel/Docker-Cron-Job-Sample.git
docker build -t edwardsp/cron-job-sample ./Docker-Cron-Job-Sample
docker run -it edwardsp/cron-job-sample