---
title: "devcontainer"
author: "James"
date: "2022-12-28"
categories: [containers]
description: Notes on devcontainer work.
---

A few weeks I took a look a vscode's devcontainer standard.
It is a standard way of building and running a docker container for development
from a specially formatted json file.

Over the holiday I played around a little bit with it.

They have a node cli program that can build, launch, and attach to the container
from the json file without vscode hosted [here](https://github.com/devcontainers/cli).

For the most part the special json file defines all the stuff you would think it does
and works as I would have expected.

The coolest thing I saw with it is they have this concept of "features".

A lot of time with Dockerfiles there is a lot of repetition with the same code repeated
in multiple Dockerfiles for different images.
There's different ways to solve this I've seen.

My custom development container handler (`dev_container`) uses
[templates](https://github.com/jpace121/dev_contain_templates/blob/master/templates/base.Dockerfile.template),
for example.

Te vscode solution has this thing called a "feature".
They build a base image from a Dockerfile like normal, and then add listed
"features" on top of the original Dockerfile.
Each feature is basically a tar file with a well known named script that the build
thing runs that can modify the original image.

I was able to write my own "feature"
[here](https://github.com/jpace121/jpace121-devcontainer-features/blob/main/src/jpace121-devel/install.sh)
which adds my normal cli stuff (like `ag` and `emacs`) to an image pretty easily.

They provide a github action to publish the features as an OCI archive, so I got
that for free basically.