Difference between Multistage vs Docker-in-Docker

Developers often confuse two important Docker concepts: multi-stage builds and Docker-in-Docker (DinD). While both involve Docker and are used in build processes, they serve different purposes and are implemented in distinct ways. Let's clarify these concepts with descriptions and examples

Multistage

Multistage build is for the developers building the docker image to use multiple stages . The main reason is to minimize the image size and practice better security as it minimizes the attack surface . There are usually multiple FROM statements for each of the stages in the build . 

Here is an example of the nodejs application built using this approach . Go application will be a better example as only the binaries will be copied to the final image , I am using nodejs for simplicity 

Github Docker Multistage

Docker-in-Docker

Docker-in-Docker refers to running a Docker daemon inside a Docker container . Its mainly used by CI/CD pipelines to build container images . This doesn't necessarily improve security , in-fact as the daemon needs to run as root it has to be run with the privileged flag ( may be the only place where this is okay ). 

It can be also used for Integration and Sanity testing as the main Docker container acts as a platform for all the other containers . You can use tools like Docker Compose to bring up multiple containers that represent different services in your application stack and run the tests . After tests are complete, you can easily tear down the entire environment, ensuring a clean slate for the next test run and improving reproducibility

here is an nodejs example demonstrating this

Github Docker-in-Docker

Containerization Github List  ->   Github Containers