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Running apache and cron in docker

I understood there should be only one process running on foreground in a docker container. Is there any chance of running both apache and cron together in foreground? A quick search says there is something called supervisord to achieve this. But is there any other method using Entrypoint script or CMD?

Here is my Dockerfile 

FROM alpine:edge
RUN  apk update && apk upgrade
RUN echo "http://dl-cdn.alpinelinux.org/alpine/edge/testing" >> /etc/apk   /repositories
RUN  apk add 
     bash  
     apache2 
     php7-apache2 
     php7 
     curl 
     php7-mysqli 
     php7-pdo 
     php7-pdo_mysql

 RUN cp /usr/bin/php7 /usr/bin/php
 RUN mkdir /startup
 COPY script.sh /startup
 RUN chmod 755 /startup/script.sh
 ENTRYPOINT ["/startup/script.sh"]

The content of script.sh is pasted below 

#!/bin/bash
# start cron
/usr/sbin/crond -f -l 8
# start apache
httpd -D FOREGROUND

When the docker is run with this image only crond is running and most interestingly when I kill the cron then apache starts and running in the foreground.

I am using aws ecs ec2 to run the docker container using task definition and a service.

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2

Answers


  1. 0

    The problem is that you’re running crond -f, without telling bash to run it in the background, basically keeping bash waiting for crond to exit to continue running the script. There’s two solutions for this:

    1. Remove the -f flag (that flag causes crond to run in the foreground).
    2. Add & at the end of the crond line, after -l 8 (I wouldn’t recommend this).

    Also, I’d start apache with exec:

    exec httpd -D FOREGROUND

    Otherwise /startup/script.sh will remain running, while it’s not doing anything useful anymore anyway. exec tells bash to replace the current process with the command to execute.

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  2. 0

    Docker container is running while main process inside it is running. So if you want to run two services inside docker container, one of them has to be run in a background mode.

    I suggest to get rid of scrip.sh at all and replace it just with one CMD layer:

    CMD ( crond -f -l 8 & ) && httpd -D FOREGROUND

    The final Dockerfile is:

    FROM alpine:edge
RUN  apk update && apk upgrade
RUN echo "http://dl-cdn.alpinelinux.org/alpine/edge/testing" >> /etc/apk/repositories
RUN  apk add 
     bash  
     apache2 
     php7-apache2 
     php7 
     curl 
     php7-mysqli 
     php7-pdo 
     php7-pdo_mysql

RUN cp /usr/bin/php7 /usr/bin/php
CMD ( crond -f -l 8 & ) && httpd -D FOREGROUND
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