A simple docker container that runs a cron invoking a shell script.
Copy the repository and build from the Dockerimage:
$ sudo docker build --rm -t docker-cron .
Run the docker container in the background (docker returns the id of the container):
$ sudo docker run -t -i -d docker-cron
b149b5e7306dba492558c7024809f13cfbb616cccd0f4020db61bf715f4db836
To check if it is running properly, connect to the container using the id and view the logfile. (You may have to wait 2 minutes)
$ sudo docker exec -i -t b149b5e7306dba492558c7024809f13cfbb616cccd0f4020db61bf715f4db836 /bin/bash
root@b149b5e7306d:/# cat /var/log/cron.log
Thu May 26 13:11:01 UTC 2016: executed script
Thu May 26 13:12:01 UTC 2016: executed script
The cron job is running. Now let's modify the interval and the actual job executed!
To change the interval the cron job is runned, just simply edit the crontab file. In default, the job is runned every minute.
* * * * * root /script.sh
To change the actual job performed just change the content of the script.sh file. In default, the script writes the date into a file located in /var/log/cron.log.
echo "$(date): executed script" >> /var/log/cron.log 2>&1