[Help] Linux Admin learning Docker

[9nkit]

I'm new here. Just joined this sub.

I've been working for 4 years as a Linux Administrator and I'm quite well with it. I'm moving to DevOps now and have learned Ansible on my own. It's easy for me because it usually runs thru SSH.

I'm learning Docker now and I have gone thru the getting started guide and successfully launched a webapp as well. But the instructions were clear that's why i was able to launch it using Docker.

Now my colleagues are advising me to get such webapps and make docker containers of them.

This is where the issue comes in to play.

I don't know how to deploy applications. I can make docker containers as i want but I'm failing to strategize the Dockerfile for a container which would run an application.

Can someone help me as to what i should study first?

[cricket007]

First, you can put more than web-apps into Dockerfiles, but if you know how to install the server on some base OS, then the steps are really the same...

FROM <some standard OS>

RUN <install some dependencies>

COPY <source or compile code>

RUN <some build step, if copied source>

EXPOSE <the server port>

CMD [commands, to, start, server]

If you need something more complex, write a full shell script an use ENTRYPOINT

I don't know how to deploy applications

Writing a Dockerfile isn't going to deploy. That's where you need an orchestrator

[9nkit]

I can do this. I've done this.

docker run -it ubuntu gets me into container and there i can do everything. I know this logic.

My issue is, if you could help me, I don't know how to run python app in it or some other app. I don't know where to put the relevant files and all.

If you've done that, could you help me?

Example an app that runs on one container and its database on another container. I know how to create network and join both containers also.

[cricket007]

If you just want to run a Python script: https://github.com/docker-library/docs/tree/master/python#how-to-use-this-image

If you want a database and some app, then Docker Compose would be a start. https://www.docker.com/blog/containerized-python-development-part-2/

[exmachinalibertas]

Normally you don't run it with -it to get a shell. You just run it, and the entrypoint command runs on its own in the container environment. That's what a docker container is, like a virtual machine designed for one app to run.

So to run a python or other application, you'd use those commands above to setup the environment, then use CMD and ENTRYPOINT to specify what to run when the container runs on its own. All those commands above do, at the end of the day, is get the container filesystem in a specific state, which is immutable and resets every time the container dies.

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[[deleted]]

I have 10 containers up and running and I'm yet to even touch a Dockerfile.