Menu
There is no such file by name entrypoint.sh in my workspace.
But below instruction in docker-compose.yml is referring it:
builder:
build: ../../
dockerfile: docker/dev/Dockerfile
volumes:
- ../../target:/wheelhouse
volumes_from:
- cache
entrypoint: "entrypoint.sh"
command: ["pip", "wheel", "--non-index", "-f /build", "."]
where ../docker/dev/Dockerfile has
# Set defaults for entrypoint and command string
ENTRYPOINT ["test.sh"]
CMD ["python", "manage.py", "test", "--noinput"]
What does entrypoint: "entrypoint.sh" actually do?
570
Introduction of Docker ENTRYPOINT. Docker entrypoint is a Dockerfile directive or instruction that is used to specify the executable which should run when a container is started from a Docker image.
Well, in essence, an EntryPoint provides a method for you to execute a command within a container, either at build time, or when the container is first run.
All About Docker Compose Override Entrypoint Entrypoint helps use set the command and parameters that executes first when a container is run. In fact, the command line arguments in the following command become a part of the entrypoint command, thereby overriding all elements mentioned via CMD.
We can also use the | operator to run multiple commands in Docker Compose. The syntax of the | operator is a bit different from the && operator. Here, we added the commands on separate lines. Everything is the same except for the command instruction.
Another option is to use a script to run entrypoint commands for the container. By convention, it often includes entrypoint in the name. In this script, you can setup the app as well as load any configuration and environment variables. Here is an example of how you can run it in a Dockerfile with the ENTRYPOINT exec syntax.
entrypoint.sh pip wheel --non-index -f /build . So basically, entrypoint.sh is a script that will run inside your container builder when you execute docker-compose up command. Also you can check this answer for more info What is the difference between CMD and ENTRYPOINT in a Dockerfile?
The ‘exec’ form allows us to specify the command line arguments to the ‘docker run’ command and it is appended to the end of all elements of the ‘exec’ form which means the specified command will run after the executable specified in entrypoint.
Entrypoint sets the command and parameters that will be executed first when a container is run. What does Entrypoint do? Entrypoint sets the command and parameters that will be executed first when a container is run.
entrypoint: "entrypoint.sh" overrides ENTRYPOINT ["test.sh"] from Dockerfile.
From the docs:
Setting entrypoint both overrides any default entrypoint set on the service’s image with the ENTRYPOINT Dockerfile instruction, and clears out any default command on the image - meaning that if there’s a CMD instruction in the Dockerfile, it is ignored.
ENTRYPOINT ["test.sh"] is set in Dockerfile describing docker image
entrypoint: "entrypoint.sh" is set in docker-compose file which describes multicontainer environment while referencing the Dockerfile.
docker-compose build builder will build image and set entrypoint to ENTRYPOINT ["test.sh"] set in Dockerfile.
docker-compose up builder will start container with entrypoint entrypoint.sh pip wheel --no-index '-f /build' . set in docker-compose file
153
ENTRYPOINT is a command or script that is executed when you run the docker container.
If you specify entrypoint in the docker-compose.yaml, it overrides ENTRYPOINT from specified Dockerfile.
CMD is something that is passed as the parameters to the ENTRYPOINT
So if you just run the dev/Dockerfile, it would execute
test.sh python manage.py test --noinput
If you overrided CMD in docker-compose.yaml as you did, it would execute
test.sh pip wheel --non-index -f /build .
But because you also overrided ENTRYPOINT in your docker-compose.yaml, it is going to execute
entrypoint.sh pip wheel --non-index -f /build .
So basically, entrypoint.sh is a script that will run inside your container builder when you execute docker-compose up command.
Also you can check this answer for more info What is the difference between CMD and ENTRYPOINT in a Dockerfile?
33
Update:
If the base image has entrypoint.sh, it will run that, but if you override with your own entrypoint then the container will run the override entrypoint.
If you to override the default behaviour of base image then you can change, ohterwise you do not need to override it from docker-compose.
What does entrypoint: "entrypoint.sh" actually do?
It totally depend on the script or command inside entrypoint.sh, but few things can be considered.
ENTRYPOINT instruction allows you to configure a container that will run as an executable. It looks similar to CMD, because it also allows you to specify a command with parameters. The difference is ENTRYPOINT command and parameters are not ignored when Docker container runs with command line parameters. (There is a way to ignore ENTTRYPOINT, but it is unlikely that you will do it.)
In simple word, entrypoint can be a complex bash script, for example in case of mysql entrypoint which is more then 200 LOC which does the following task.
So much complex task is not possible with CMD, as in CMD you can run the bash but it will be more headache to make it work. Also it make Dockerfile simple and put the complex task to entrypoint.
When there is entrypoint, anything that is passed to CMD will be consider as a argument for entrypoint.
In your case, CMD is CMD ["python", "manage.py", "test", "--noinput"] it will be passed as an argument and the best to run this is to use use
# set of command
#start long running process at the end that is passed from CMD
exec "$@"
Finally, the exec shell construct is invoked, so that the final command given becomes the container's PID 1.
$@is a shell variable that means "all the arguments",
use-a-script-to-initialize-stateful-container-data
cmd-vs-entrypoint
2
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
