Docker basics

Docker Basics

Docker’s networking structure

• 27. Docker Networks: Concepts for Private and Public Comms in Containers
  • docker 네트워크 구조에 대해 그림으로 설명해준다.

Docker Image naming convention

user/repo:tag

• official image에는 user가 생략된다.

Dockerfile

• FROM (image name)
• ENV (variable name) (value)
• WORKDIR (path)
• RUN (command)
• EXPOSE (port…)
• CMD [“command”]

Dockerfile의 기본 네이밍은 Dockerfile

• 다른 이름으로 만들수도 있다. 다만 실행할 때는 -f 옵션과 함께 사용.

Persistent Data: Bind Mounting

• Maps a host file or directory to a container file or directory
• Mounting된 볼륨은 실시간 동기화된다.

Docker Compose

사용하는 이유

• Configure relationships between containers

Docker Compose는 두가지로 구성된다.

1. YAML-formatted file that describes our solution options for
   • containers
   • networks
   • volumes
2. A CLI tool docker-compose used for local dev/test automation with those YAML files.

Docker Compose file naming convention

• docker-compose.yml is default filename but any can be used with docker-compose -f

Docker Healthchecks

• HEALTHCHECK is supported in DOckerfile, Compose YAML, docker run, and Swarm Services.
• It is running inside of our container, so we can healthcheck a container that has not a exposed port.
• exit 0 (OK)
• exit 1 (Error)
• Three container states: starting, healthy, unhealthy

To do Healthcheck

• need to add option to Dockerfile like:
  • HEALTHCHECK curl -f http://localhost/ || false

HEALTHCHECK --timeout=2s --interval=3s --retries=3 \
  CMD curl -f http://localhost/ || exit 1