Containerized processes are configured using environment variables:
docker run -d --name mysql mysql
docker logs mysql
The container read environment variables and changes its behaviour:
docker run -d --name mysql2 --env MYSQL_RANDOM_ROOT_PASSWORD=yes mysql
docker logs mysql2
ENTRYPOINT vs. CMDCMD configured the default command:
$ cat Dockerfile.cmd
FROM ubuntu
CMD [ "ps" ]
$ docker build --file Dockerfile.cmd --tag cmd .
$ docker run -it --rm cmd
ENTRYPOINT receives CMD as parameters:
$ cat Dockerfile.entrypoint
FROM ubuntu
ENTRYPOINT [ "ps" ]
CMD [ "faux" ]
$ docker build --file Dockerfile.entrypoint --tag entrypoint .
$ docker run -it --rm entrypoint
Add an entrypoint to change the behaviour
Example: Change text in web page
docker build \
--tag my-nginx \
.
docker run --detach \
--publish 127.0.0.1:80:80 \
--env WELCOME_TO_TEXT="Haufe X360" \
my-nginx
curl localhost
Change configuration of nginx in /etc/nginx