Where can I learn Docker fundamentals?

Submitted ⁨⁨1⁩ ⁨year⁩ ago⁩ by ⁨dartanjinn@lemm.ee⁩ to ⁨selfhosted@lemmy.world⁩

I jumped into Docker feet first a few months ago and have had a real good time with it. Networking doesn’t make sense, I dlcanr ever seem to access config files without dropping to su -, all the tutorials and videos I find are pretty top level and assume the user already has a firm grasp on it. It’s great for drop in stuff like open speed test and Vaultwarden but I recently tried setting up dashy and I can’t even find the config files to edit. The Dashy documentation says the easiest way to edit the configs is to use code-server, so I spun up a code-server VM and can’t even get it to open the files because the web based VSC doesn’t allow for SSH editing. There’s nothing explained in the documentation beyond that.

Yes I’m frustrated but I’m not bitching as if these solutions are trash, I’m simply asking where can I go to learn this shit from the ground up? It doesn’t make any sense to me from the perspective that I’ve approached it. Networking seems to be silly and weird, entering an interactive TTY to the container seems to be useless as there’s no package manager and doesn’t seem to have vim, nano, or any native way to edit configs. It’s been extremely frustrating so I ask you, where can I learn what I’m doing wrong and how to properly work with Docker?

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ryapric@lemmy.world ⁨1⁩ ⁨year⁩ ago
Echoing the sentiment that you should adjust your perspective in approaching containerization, otherwise you’re in for a tough time.

Jerome Petazzoni, one of the more recognizable names in the container community, has a site where he puts all of his workshops, slides, etc. This is his one for getting started with Docker.

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- dartanjinn@lemm.ee ⁨1⁩ ⁨year⁩ ago
  Huge thanks for this. I’ll look at them tonight.
  
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- spez_@lemmy.world ⁨1⁩ ⁨year⁩ ago
  Is there a PDF
  
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flubba86@lemmy.world ⁨1⁩ ⁨year⁩ ago
Sounds like you, like a lot of others, have come to docker from the perspective of “it’s like a mini virtual machine”. Maybe you’ve used VMs before, like virtualbox or VMware or EC2. Maybe you have experience with setting up a cluster of VMs, each with their own OS, own SSH client, own suite of applications, and an overlay network between them all. Maybe someone told you “you should use docker instead, it’s like mini lightweight VMs”. And you’d be right to assume this is the wrong perspective to approach docker, because it leads to the problems you have faced.

Instead, try to think of docker containers as standalone applications. They don’t contain a kernel, they don’t have SSH, no Nano or VIM, just simply the Application, in a container, with enough supporting filesystem and OS libraries to make the application work.

That perspective is what helped me to get better at docker, I know it’s not exactly answering your question, but it might help.

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- dartanjinn@lemm.ee ⁨1⁩ ⁨year⁩ ago
  “like mini lightweight VMs”
  
  That’s exactly how I’ve approached it cause that’s exactly how it was explained. But it’s not at all like that. Thanks for your explanation.
  
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  - flubba86@lemmy.world ⁨1⁩ ⁨year⁩ ago
    Same, that’s how it was explained to me too. It spent over a year learning docker the wrong way, and trying to use it as a replacement for VMs, after a coworker told me that.
    
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housepanther@lemmy.goblackcat.com ⁨1⁩ ⁨year⁩ ago
I started learnin docker first by how to customize an image. Since Alpine Linux is a popular light weight distro, I started with customizing it and moved from there. I also explored other people’s Dockerfiles to see how to use a Dockerfile to customize an image to containerize an app.

I found almost every YouTube howto on the subject matter very frustrating and often making the assumptions that you note. I also read the reference documentation on docker’s website. It’s not easy and it’s time consuming. I’d say I am good enough to be dangerous, not much more than that. Mostly, I’ve modified other people’s images to suite my needs

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- dartanjinn@lemm.ee ⁨1⁩ ⁨year⁩ ago
  Thanks I’ll look into that. It doesn’t help that my introduction to Docker was using portainer so I haven’t really had much experience in the terminal outside of docker ps. I really put the cart before the horse there and am regretting it.
  
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  - housepanther@lemmy.goblackcat.com ⁨1⁩ ⁨year⁩ ago
    Hey, it’s okay. I’ve been there and done that myself. You’ll find it useful to look at both Dockerfile and docker-compose.yml files. A mistake I made early on was thinking I could replace a Dockerfile with a docker-compose.yml one. The Dockerfile itself describes how an image should be built. The docker-compose.yml file describes the environment and fetches images. It also may pass variables to the Dockerfile.
    
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Ducks@ducks.dev ⁨1⁩ ⁨year⁩ ago
This might not be a popular opinion, but I had a very short period of time between graduating school and starting work where I needed to learn docker and I found this course: serversforhackers.com/shipping-docker to be very helpful, they had a sale and I got the course and it taught me everything I needed in a few days.

You absolutely don’t need a course to learn it, but sometimes these can be easy shortcuts.

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ColdCreasent@lemmy.ca ⁨1⁩ ⁨year⁩ ago
Lots of great information and suggestions in this discussion. Thank you everyone who are offering your input. I’d like to ask as well, how easy is it to setup docker for use in windows? I ask this because almost every guide I’ve found has docker running in Linux. I realize you are able to setup a docker in windows, but I was struggling to get basic instructions for windows, and even the tutorial in docker required me to switch back to docker types that don’t work in windows.

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- nekusoul@lemmy.nekusoul.de ⁨1⁩ ⁨year⁩ ago
  From my experience the “default” experience, which is Docker Desktop, is a pain, due to what you described. In particular, Linux containers and Windows file permissions just don’t mix well.
  
  Other than that, there’s three options:
  
  Docker Desktop, but used from WSL 2. This seems to be the cleanest solution nowadays. Never personally used it though. Officially supported.
  
  Installing Docker inside WSL 2. Configuring this correctly is a bit of a pain and not really supported AFAIK.
  
  Installing Docker in a VM, using the integrated Hyper-V functionality for example. The least amount of integration, but most reliable.
  
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  - ColdCreasent@lemmy.ca ⁨1⁩ ⁨year⁩ ago
    And WSL 2 is the “Linux within windows” if I recall. And your other recommendation is a Linux vm with dockers running inside it? I’ll give that a try if I decide to switch to dockers again instead of just a vm. My original use case was to have a downloader and vpn bundled inside one docker so the rest of the system doesn’t see the vpn connection, but decided to use a vm to accomplish it instead due to “windows+docker” issues.
    
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NegativeLookBehind@kbin.social ⁨1⁩ ⁨year⁩ ago
Containers are hard. This should at least get docker running without sudo: https://www.baeldung.com/linux/docker-run-without-sudo

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- Falmarri@lemmy.world ⁨1⁩ ⁨year⁩ ago
  This is almost worse than using sudo. Because now you essentially have full sudo access without having the protections of sudo, like asking for your password
  
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- subtext@lemmy.world ⁨1⁩ ⁨year⁩ ago
  Podman is supposed to be a sudo-less container solution. Though fair warning I hear it is also quite frustrating to start.
  
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  - PriorProject@lemmy.world ⁨1⁩ ⁨year⁩ ago
    Rootless podman (or docker) is a very different thing that adding yourself to the docker group. Rootless is an advanced topic that makes networking and other fundamental aspects of the container runtime work differently so it’s harder to exploit the runtime itself. Adding yourself to the docker group just gives your account permission access the docker daemon running as root… which is a much less fundamental change.
    
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  - dartanjinn@lemm.ee ⁨1⁩ ⁨year⁩ ago
    Yeah I spent a few hours with Podman before I went straight back to Docker.
    
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nekusoul@lemmy.nekusoul.de ⁨1⁩ ⁨year⁩ ago
It doesn’t make any sense to me from the perspective that I’ve approached it.

I think you’ve already identified the issue. Docker is pretty “simple”, but you’ve got to approach it from the right angle or else it doesn’t make sense. Apart from suggesting the official documentation I can’t give you much advice on how to learn it because my path to understanding Docker was pretty much just trying things out and iterating on it. That said here’s a tips that could help:

If you aren’t using Docker Compose already, you really should. Just having your entire configuration for a service in a single file really helps.

Aside from debugging, you normally aren’t meant to run commands manually in a container. It’s best to act like every container is just a black box that simply does its thing.

If you need to edit config files, the easiest way is to just directly on the host if you’re using bind mount volumes, or spin up a temporary container running Debian or Alpine for example that also has the Docker Volume mounted.

As @housepanther@lemmy.goblackcat.com has already mentioned, building your own images is also pretty helpful since it strips a lot of the “black magic” away and teaches you how to further “mod” existing images.
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DontAskAboutUpdog@lemmy.world ⁨1⁩ ⁨year⁩ ago
Start by making a simple image and make a container of it (I started with a simple python webserver)

Once you grasp basic cli commands and the docker lingo, try pulling portainer and use its web ui.

Next step would be to customize an image.

There is a lot of information on SO, and you can ask specific questions on sites like this one. YT videos are 99% shit. Avoid.

I think docker is so stupidly awesome I nowdays dont want to do anything without it.

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macallik@kbin.social ⁨1⁩ ⁨year⁩ ago
I've been using my library's membership to LinkedIn Learning to take a Docker Essentials course

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- dartanjinn@lemm.ee ⁨1⁩ ⁨year⁩ ago
  I think that might be exactly what I was looking for. Thank you.
  
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Oisteink@feddit.nl ⁨1⁩ ⁨year⁩ ago
You need to understand the fundamentals of how containers work. What’s inside the container is up to the creator - if you are the creator and want a package manager in there just install it. Normal way for me would be to pick a container for a system I like and add my own stuff. Find one that has what you want and add your stuff there.

Tldr: take your example and ask ChatGPT about the parts you don’t understand

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unscholarly_source@lemmy.world ⁨1⁩ ⁨year⁩ ago
I took a look at Dashy, I think I see the confusion. If you are looking at this article, then yes they mention Code Server, but that’s purely in the context of using Dashy in a non-docker context. But to be honest, any text editor works.

But I think that’s a red herring. That in itself has nothing to do with docker.

What you’ll need to do, once you understand the fundamentals of running docker, pull images, start a container based on an imagine, is to expose a docker volume that points to /public/conf.yaml. A docker volume ensures that the file or directory it’s mapped to in the container is available and persists outside of the container. This allows you to persist files and directories without losing them once the container stops or restarts.

Once the volume is exposed, then you can use your favorite text editor to update the dashy config file. Code Server is fine, powerful, but overkill.

But first, try getting familiar with pulling, starting stopping docker images using the cli. Gotta start there first before tinkering with docker parameters like volumes.

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- dartanjinn@lemm.ee ⁨1⁩ ⁨year⁩ ago
  Yeah Dashy isn’t really important to me, it’s just another fun project to learn more about Docker. However, what I learned is that I don’t know shit about what I’m doing lol. It proved to be a great tool at exposing my absolute ignorance of something I thought I was getting a good grasp on.
  
  Yeah I think I’m gonna shit can Portainer and go through that LinkedIn course someone else posted. Thanks for your insight.
  
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redcalcium@lemmy.institute ⁨1⁩ ⁨year⁩ ago
Some pointers that might help you:

You can mount the same directory in multiple containers. So you can totally have a container reading files from a directory, and access the same files on that directory from, say, a VSCode server container. Just make sure the container both use the same UID and GID to prevent permission issues.

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