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istepanov/cron

By istepanov

•Updated over 8 years ago

Docker container that runs cron. Use this a base image for your periodic task containers.

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istepanov/cron repository overview

⁠istepanov/cron

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Docker image that runs cron that periodically executes bash script.

⁠Usage
docker run [-d] [-e 'CRON_SCHEDULE=...'] istepanov/cron [no-cron] command
⁠Base image parameters
  • -e 'CRON_SCHEDULE=0 1 * * *': specifies when cron job starts (details⁠). Default is 0 1 * * * (runs every day at 1:00 am).
  • no-cron: if specified, run container once and exit (no cron scheduling).
  • command: the actual command that will be run by cron job.
⁠Example

Print 'Hello World!' every minute:

docker run -e 'CRON_SCHEDULE=* * * * *' istepanov/cron echo 'Hello World!'

Do it in the background:

docker run -d -e 'CRON_SCHEDULE=* * * * *' istepanov/cron echo 'Hello World!'

Run immediately once:

docker run -e 'CRON_SCHEDULE=* * * * *' istepanov/cron no-cron echo 'Hello World!'
⁠Advanced example - build your own image based on this image

Let's build an image that will run Docker-flavored cowsay periodically.

Dockerfile

FROM istepanov/cron

RUN apk add --no-cache perl ca-certificates wget && \
    wget -O /usr/local/bin/cowsay https://raw.githubusercontent.com/docker/whalesay/master/cowsay && \
    mkdir -p /usr/local/share/cows && \
    wget -O /usr/local/share/cows/default.cow https://raw.githubusercontent.com/docker/whalesay/master/docker.cow && \
    chmod +x /usr/local/bin/cowsay && \
    apk del wget ca-certificates

command.sh

#!/bin/bash

cowsay "$COW_SPEECH"

Build the image:

docker build -t cowsay .

Run the image in background:

docker run -e 'CRON_SCHEDULE=* * * * *' -e COW_SPEECH='Hello World!' cowsay

Output:

Job started: Fri Oct  6 04:48:00 UTC 2017

< Hello World! >
 --------------
    \
     \
      \
                    ##         .
              ## ## ##        ==
           ## ## ## ## ##    ===
       /"""""""""""""""""\___/ ===
      {                       /  ===-
       \______ O           __/
         \    \         __/
          \____\_______/

Job finished: Fri Oct  6 04:48:00 UTC 2017
Job started: Fri Oct  6 04:49:00 UTC 2017
 ______________
< Hello World! >
 --------------
    \
     \
      \
                    ##         .
              ## ## ##        ==
           ## ## ## ## ##    ===
       /"""""""""""""""""\___/ ===
      {                       /  ===-
       \______ O           __/
         \    \         __/
          \____\_______/

Job finished: Fri Oct  6 04:49:00 UTC 2017

Tag summary

Content type

Image

Digest

Size

3.2 MB

Last updated

over 8 years ago

docker pull istepanov/cron