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---
title: Developing with Docker
author: gitlab.com/xlgmokha/developing-with-docker
date: 2020-06-10
---
# Developing with Docker
Mo Khan, Backend Engineer
Composition Analysis, GitLab
https://gitlab.com/xlgmokha
Inspired by: gitlab-org/gitlab#216082
# Agenda
* Build (build)
* Start/Stop container (ps, start, stop)
* Getting a shell (run vs exec)
* Analyzing an image (dive, docker layers)
* Shrinking an image (compression, discuss the trade offs of having more v. less layers)
* Sharing an image (push, pull, authn)
# Definitions
* Image: is like a class
* Container: is like an instance of a class (i.e. object)
# Definitions - Image/Container
* Person is a class definition
* "you" and "mo" are instances of the class Person
* instances of person can interact with one another
```ruby
class Person
def fist_bump(other_person)
end
end
mo = Person.new
you = Person.new
mo.first_bump(you)
```
# Definitions
Registry: stores images and makes them available to others
For example:
* https://index.docker.io
* https://registry.gitlab.com
```bash
curl -s -i https://index.docker.io/v2/alpine/tags/list
```
# Docker - Architecture
```plantuml
```
https://docs.docker.com/get-started/overview/#docker-architecture
# Dockerfile
A minimal Dockerfile:
```file
path: examples/001/Dockerfile
relative: true
lang: docker
```
https://docs.docker.com/engine/reference/builder/
# Dockerfile - FROM
> Initializes a build stage and sets a Base Image.
In this example the base image is alpine:latest.
By default this image will be fetched from the default Docker registry.
https://index.docker.io/
```file
path: examples/001/Dockerfile
relative: true
lang: docker
lines:
start: 0
end: 1
```
# Dockerfile - COPY
Copy "hello.rb" from the host to
"/usr/local/bin/hello" within the Docker image.
```file
path: examples/001/Dockerfile
relative: true
lang: docker
lines:
start: 1
end: 2
```
```terminal8
tree ./examples/001
```
# Dockerfile - RUN
RUN a command from within the image and make "hello" executable.
```file
path: examples/001/Dockerfile
relative: true
lang: docker
lines:
start: 2
end: 3
```
# Dockerfile - CMD
Set the default command to run when the docker image
is launched as a container.
```file
path: examples/001/Dockerfile
relative: true
lang: docker
lines:
start: 2
end: 3
```
# docker build
```terminal32
bash -il
```
# docker ps
# docker start
# docker stop
# docker run
# docker exec
# dive
* Describe layers
* Downloading multiple layers in parallel vs 1 large layer
# Compression (zstd)
More layers == more parallel download
Smaller layers == faster downloads
# Distribution
# docker push
# docker pull
# docker login
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