I wanted to explore linux namespaces and understand how docker works internally.

This project is a toy docker implementation in C

• An overlayfs is used to create containers from images, thereby saving time on extraction of the image.
• Uses pivot_root to change the root of the container
• Creates a new UTS, PID and NET namespace for the container
• A veth pair is used to connect the container to an existing docker0 bridge

First compile the application

$ gcc -O3 main.c run.c utils.c container.c -o container -std=gnu11

Then run the program with

$ sudo ./container run <image_name> <command>

Example:

$sudo ./container run ubuntu bash

Note: The image file must be present in the images/ directory with the following structure images/<image_name>.tar.gz

The image file must be a compressed root filesystem

Get an alpine linux image from here and save it as images/alpine.tar.gz

For example, images/ubuntu.tar.gz

• Better handling of command line arguments
• Command to build, create, view and download containers and images
• Create a new bridge with routing instead of reusing docker0
• Configuration files
• cgroups, setuid and seccomp

This project is based on https://github.com/Fewbytes/rubber-docker, but is implemented in C.