Docker Cron Jobs — Run Scheduled Tasks in Containers

Running cron jobs in Docker containers uses standard 5-field cron syntax, but requires some container-specific setup.

Common approaches:

1. Cron inside the container:

FROM alpine:latest
RUN apk add --no-cache dcron
COPY crontab /etc/crontabs/root
CMD ["crond", "-f", "-d", "8"]

2. Docker host cron calling docker exec:

0 0 * * * docker exec my-container /app/daily-job.sh

3. Using a sidecar scheduler (like Ofelia or supercronic):

services:
  scheduler:
    image: mcuadros/ofelia:latest
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock

Key considerations:

• Container cron doesn't have access to environment variables by default
• Logs go to container stdout/stderr
• Use supercronic for better container-native cron behavior
• For Kubernetes, use CronJobs instead of in-container cron