I want to be able to run a simple bash script within a container service on the hour using cron. I'm using Alpine Linux via docker-compose
with a custom Dockerfile to produce a php-fpm based image, on which I hope to get crond
running as well - except I can't.
Executing ps aux | grep cron
on the container once built, returns nothing.
From what I understand, the usual Linux startup processes don't exist in Docker containers - fine - so how do I auto-start crond
? Its dirs under /etc/periodic/
are created automatically, so I don't understand why the applicable process that consumes those dirs, isn't also running.
I tried creating a dedicated service definition within docker-compose.yml
, which actually worked but the shell script to be run hourly needs access to a php binary which is running in a different container, so this isn't a viable solution.
If I shell into the container and run rc-service crond start
I get this - but it never "finishes":
/var/www/html # rc-service crond start
* WARNING: crond is already starting
#> docker --version
Docker version 19.03.8, build afacb8b7f0
#> docker-compose --version
docker-compose version 1.23.2, build 1110ad01
I need a solution that I can place into my Dockerfile
or docker-compose.yml
files.
Dockerd is running on Ubuntu Xenial FWIW.
to run a cronjob container (Alpine), you need to make sure sure that the command of your docker container is
exec crond -f
if you want to add this to a docker file
CMD ["exec", "crond", "-f"]
you also may need to update the corn files before running the above command
To be able to solve your issues you need to update your docker-compose to have two containers one for cron and one for web
service_php_cron:
build:
context: .
dockerfile: .docker/services/php/Dockerfile.dev
container_name: base_service_php
command: 'cron_jobs'
volumes:
- ./app:/var/www/html/public
env_file:
- ./.env
# Low level container logging
logging:
driver: "json-file"
options:
max-size: "1m"
max-file: "5"
service_php:
build:
context: .
dockerfile: .docker/services/php/Dockerfile.dev
ports:
- "9000:9000"
command: 'web_server'
container_name: base_service_php
volumes:
- ./app:/var/www/html/public
env_file:
- ./.env
# Low level container logging
logging:
driver: "json-file"
options:
max-size: "1m"
max-file: "5"
you also need to update your docker file to be able to handle multiple commands using docker entry points
Add the below line to your docker file + remove the CMD one
COPY ./docker-entrypoint.sh /
RUN chmod a+x /docker-entrypoint.sh
ENTRYPOINT ["/docker-entrypoint.sh"]
and finally, create the entry point (make sure it hash execute permissions)
#!/bin/sh -e
case $1 in
web_server)
YOUR WEB SERVER COMMAND
;;
cron_jobs)
exec crond -f
;;
*)
exec "$@"
;;
esac
exit 0
you can check this link for more info about entrypoints