docker-cron-swissknife
Alpine based dockerfile that allows to register and execute cron tasks with ease.
It can:
- Run host system's docker binary and execute commands against it (given proper mounts).
- Mount cron jobs from a shared volume on host
- Create cron jobs from environment variable
Environment variables:
-
CRON_STRINGS - add cronjobs as environment variables. Example:
CRON_STRINGS=* * * * * /any-command-you-wishYou can put multiple commands in CRON_STRINGS. Just use "\n" for newline.
-
CRON_TAIL - if defined cron log file will be read to STDOUT by tail. By default cron runs in foreground mode.
Mount cron files from host:
You can mount files from host as: /path/to/host/crontabs:/etc/cron.d, when container starts, it will copy all files from /path/to/host/crontabs into /etc/cron.d
Where are my logs?
By default log files are placed in /var/log/cron/cron.log
Usage example:
Without access to host Docker:
docker run -d \
-v /path/to/host/crontabs:/etc/cron.d \
timonweb/docker-cron-swissknife:non-stable
With access to host Docker:
docker run -d \
-v /path/to/host/crontabs:/etc/cron.d \
-v /var/run/docker.sock:/var/run/docker.sock \
-v /usr/bin/docker:/usr/bin/docker \
timonweb/docker-cron-swissknife:non-stable
With cronjob defined via environment variable:
docker run -d \
-v /path/to/host/crontabs:/etc/cron.d \
-v /var/run/docker.sock:/var/run/docker.sock \
-v /usr/bin/docker:/usr/bin/docker \
-e 'CRON_STRINGS=* * * * * docker ps' \
timonweb/docker-cron-swissknife:non-stable
As a service in docker-compose.yml:
cron:
image: timonweb/docker-cron-swissknife:non-stable
volumes:
- "/var/run/docker.sock:/var/run/docker.sock"
- "/usr/bin/docker:/usr/bin/docker"
environment:
- CRON_STRINGS=* * * * * docker ps
Special thanks
This Dockerfile was inspired by: https://github.com/xordiv/docker-alpine-cron, many thanks to xordiv for the idea.
Copyright
Copyright (c) 2018 Tim Kamanin https://timonweb.com