Docker quits after script has been executed - bash

Question

I have docker container starting with command:
"CMD [\"/bin/bash\", \"/usr/bin/gen_new_key.sh\"]"
script looks like:
#!/bin/bash
/usr/bin/generate_signing_key -k xxxx -r eu-west-2 > /usr/local/nginx/s3_signature_key.txt
{ read -r val1
read -r val2
sed -i "s!AWS_SIGNING_KEY!'$val1'!;
s!AWS_KEY_SCOPE!'$val2'!;
" /etc/nginx/nginx.conf
} < /usr/local/nginx/s3_signature_key.txt
if [ -z "$(pgrep nginx)" ]
then
nginx -c /etc/nginx/nginx.conf
else
nginx -s reload
fi
Script is working itself as I can see all data in docker layer in /var/lib/docker..
It is intended to run it by cron for every 5 days as AWS signature key generated in first line is valid for 7 days only. How can I prevent Docker to quit after script is finished and keep is running?

Answer 1

You want a container that is always ON with nginx, and run that script every 5 days.
First you can just run nginx using:
CMD ["nginx", "-g", "daemon off;"]
This way, the container is always ON with nginx running.
Then, just run your script as a usual script with the cron:
chmod +x script.sh
0 0 */5 * * script.sh
EDIT: since the script must be running in the first time
1) one solution (the pretty one), it's to load manually the AWS valid signing key the first time. After that first time, the script will update the AWS valid signing key automatically. (using the solution previously presented)
2) the other solution, it's to run a docker entrypoint file (that it's your script)
# Your script
COPY docker-entrypoint.sh /usr/local/bin/
RUN ["chmod", "+x", "/usr/local/bin/docker-entrypoint.sh"]
ENTRYPOINT ["/usr/local/bin/docker-entrypoint.sh"]
# Define default command.
CMD ["/bin/bash"]
On your script:
service nginx start
echo "Nginx is running."
#This line will prevent the container from turning off
exec "$#";
+ info about reason and solution to use the exec line