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gocker

A minimal psudo-Docker implementation heavily inspired by Liz's Rice containers-from-scratch. This was meant to be a learning exercise after seeing her GOTO 2018 talk titled "Containers From Scratch" and being inspired to further that learning. Much of the base code is from her work and I especially recommend that you check out both the code and the talk!

Liz Rice's GOTO 2018 talk titled Containers From Scratch

Running a Container

Note: Gocker must be ran as root

To run a command in a container, the command is constructed as follows:

sudo ./gocker run [IMAGE_OWNER/]IMAGE_NAME[:TAG] [COMMAND]

By this, I mean that the image owner, the tag, and the command to run are all optional.

  • IMAGE_OWNER - Currently Gocker assumes use of Docker Hub. If you are using an official library image, such as the ubuntu image, you may omit this and Gocker assumes it's an official library image.
  • TAG - If omitted, Gocker assumes that it will either use the latest tag, or if that doesn't exist, the last tag provided by the Docker Hub API when querying the tags for the image
  • COMMAND - If omitted, Gocker will defer to using either the CMD or Entrypoint defined in the containers manifest

For example, since the official Ubuntu image on Docker Hub has a CMD defined as bash, you could simply run the following and be dropped into a Bash shell:

sudo ./gocker run ubuntu

Alternatively, you can provide a tag and a command to run if you'd prefer:

sudo ./gocker run ubuntu:22.10 echo hello Gocker

2022/07/10 00:47:04 Running  [echo hello Gocker]  on image  ubuntu:22.10
# Logging omitted for brevity
hello Gocker

Or for an exmaple for a non-library image with a tag and a command:

sudo ./gocker run bitnami/kubectl:1.24 /bin/bash

2022/07/10 00:50:11 Running  [/bin/bash]  on image  bitnami/kubectl:1.24
# Logging omitted for brevity
root@5ZWP5YxLkr4milfpoYNT0erLaDWXDEpS:/ kubectl version

Client Version: version.Info{Major:"1", Minor:"24", GitVersion:"v1.24.2", GitCommit:"f66044f4361b9f1f96f0053dd46cb7dce5e990a8", GitTreeState:"clean", BuildDate:"2022-06-15T14:22:29Z", GoVersion:"go1.18.3", Compiler:"gc", Platform:"linux/amd64"}
Kustomize Version: v4.5.4

Current Limitations

  1. Only works with Docker Hub for the container registry
  2. There is no networking