docker-cron

Dead simple crontab container for running scheduled commands in Docker.

Features

• Simple and lightweight cron job runner
• Immediate execution option
• Package installation support
• Real-time log viewing
• Secure by default
• Human-readable cron schedule explanations

Usage

Docker Compose

version: '3.9'

services:
  cron:
    image: betterweb/cron:latest
    command: "curl https://example.com/cron.txt"
    environment:
      - CRON_SCHEDULE="*/5 * * * *" # Run every 5 minutes
      - CRON_APTS="curl"
      - CRON_IMMEDIATE="false"

Docker run:

sudo docker run -e "CRON_SCHEDULE=* * * * *" -e "CRON_APTS=curl" -e "CRON_IMMEDIATE=false" betterweb/cron:latest "curl https://example.com/cron.txt"

Security Features

• Runs cron jobs as non-root user 'crontab'
• Minimal base image with only required packages
• Proper file permissions for cron jobs
• Uses gosu for proper privilege dropping

Environment Variables

• CRON_SCHEDULE: Cron schedule expression (required)
• CRON_APTS: Space-separated list of additional packages to install (optional)

Cron Schedule Format Guide

The CRON_SCHEDULE must contain all 5 components:

┌───────────── minute (0 - 59)
│ ┌───────────── hour (0 - 23)
│ │ ┌───────────── day of month (1 - 31)
│ │ │ ┌───────────── month (1 - 12)
│ │ │ │ ┌───────────── day of week (0 - 6) (Sunday to Saturday)
│ │ │ │ │
* * * * *

Common Examples:

• Every minute: * * * * *
• Every 5 minutes: */5 * * * *
• Every hour: 0 * * * *
• Every day at midnight: 0 0 * * *
• Every Monday at 3am: 0 3 * * 1

Special Characters:

• * : any value
• */n: every n intervals
• n-m: range from n to m
• n,m: specific values n and m

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

MIT