Python Docker 容器中的 Cron 作业

Question

I have three files which is

• crontab: lists of cron job to be execute

• entrypoint.sh

   #!/usr/bin/env bash

  service cron start python

and docker file basically to install the pip and to run crontab on certain folder.

My question is: Why in my docker container, the cron just start once and Exited. have no ways to find the logs of it as it shows: Starting periodic command scheduler: cron.

i wish to know whats the proper way of setting up and how to keep it running.

Thanks

Answer 1

There are multiple ways on how you can run a cronjob inside a docker container. Here is an example for a cron-setup on debian using cronjob files .

Create a crontab file

  * * * * * root echo "Test my-cron" > /proc/1/fd/1 2>/proc/1/fd/2

my-cron - This file contains the interval , user and the command that should be scheduled. In this example we want to print the text Test my-cron every minute.

Create a docker entrypoint

#!/usr/bin/env bash

cron                   # start cron service

tail -f /dev/null      # keep container running

entrypoint.sh - This is the entrypoint which gets executed when the container gets started.

Create a Dockerfile

FROM debian:latest

RUN apt-get update \ 
    && apt-get install -y cron

# Cron file
ADD ./my-cron /etc/cron.d/my-cron
RUN chmod 0644 /etc/cron.d/my-cron

# Entrypoint
ADD ./entrypoint.sh /usr/bin/entrypoint.sh
RUN chmod +x /usr/bin/entrypoint.sh

CMD [ "entrypoint.sh" ]

Run

Build the image

docker build . --tag my-cron

Start a container

docker run -d my-cron:latest

Check the console output

docker logs <YOUR_CONTAINER_ID> --follow