How to run a cron job inside a Docker container

Question

I tried to run a cron job inside a Docker container

but nothing works for me

my container have only cron.daily and cron.weekly file

crontab,cron.d,cron.hourly ... are absent in my container

crontab -e also not working

my container runs with /bin/bash

Answer 1

I would like to give an example of how I created a cron job so that you can implement your own. To run cron container first create the following files:-

crontab.txt

entry.sh

script.sh

Dockerfile

See the following what should be in the files as mentioned above.

crontab.txt

*/30 * * * * /script.sh >> /var/log/script.log

Entry.sh

#!/bin/sh

# start cron

/usr/sbin/crond -f -l 8

script.sh

#!/bin/sh

# code goes here.

echo "This is a script, run by cron!"

Dockerfile

FROM alpine:3.3

ADD crontab.txt /crontab.txt

ADD script.sh /script.sh

COPY entry.sh /entry.sh

RUN chmod 755 /script.sh /entry.sh

RUN /usr/bin/crontab /crontab.txt

CMD ["/entry.sh"]

Then, build the docker file using the following commands 

Sudo docker build <dockerfile-name> . 

Sudo docker run -d <dockerfile-name>

Thus, we can build a cron job inside a Docker container. So now you can easily implement by following through this.

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