Images & Containers: The Core Building Blocks

Build & Run basic image with Dockerfile

FROM node:14
WORKDIR /app
COPY . .
RUN npm install
EXPOSE 3000
CMD [ "node", "app.mjs" ]

docker build -t getting-started:v1 .

docker run -dp 3000:80 getting-started:v1

Images are Read-Only

Nên là mỗi khi update code, application => create new image => run => container with new version of code

Images Layers

FROM node:14
WORKDIR /app
COPY . .
RUN npm install
EXPOSE 3000
CMD [ "node", "app.mjs" ]

  • Với cái Dockerfile như trên nếu chúng ta build lại image mà không thay đổi code => nó có cache để không phải chạy lại. Tuy nhiên khi mà ta đã thay đổi code thì nó sẽ chạy lại các instructions kể từ chỗ đã thay đổi đến hết.

  • Do đó để save time, ta sẽ làm như sau với case này:

FROM node:14
WORKDIR /app
COPY package.json .
RUN npm install
COPY . .
EXPOSE 3000
CMD [ "node", "app.mjs" ]

Attach & Detach Container

Attach

docker attach <id-name>

trường hợp cần thêm thông tin từ việc chạy docker => attach hoặc dùng docker

Detach

docker run -p 8000:80 -d <id-name>

If you started a container in detached mode (i.e. with -d), you can still attach to it afterwards without restarting the Container with the following command: docker attach CONTAINER

Internative mode

Example:

from random import randint

min_number = int(input('Please enter the min number: '))
max_number = int(input('Please enter the max number: '))

if (max_number < min_number): 
  print('Invalid input - shutting down...')
else:
  rnd_number = randint(min_number, max_number)
  print(rnd_number)

Dockerfile:

FROM python
WORKDIR /app
COPY . .
CMD ["python", "rng.py"]

Nếu run bình thường ta sẽ không thể tương tác, input vào được do đó ta cần 2 options:

 -i, --interactive                    Keep STDIN open even if not attached
 -t, --tty                            Allocate a pseudo-TTY

option -i => cho phép stdin, -t giả lập => terminal để tương

Remove

  • Chỉ được xóa container mà đã stop

docker rm CONTAINER

  • Chỉ được xóa image mà không được dùng ở bấn kì container nào

docker rmi

docker image prune

  • Sẽ xóa toạn bộ các image không sử dụng

  • Thêm option -rm => vào docker run thì container sẽ được xóa khi bị stop 1 cách auto

More information about an image

docker image inspect IMAGE-

Copy file into & from container

docker cp source CONTAINER-NAME:dest

Name & Tag of Containers & Images

  • Thêm option --name trong câu lệnh docker run:

docker run -p 8000:80 -d --name NAME IMAGE-NAME:TAG

  • Thêm option -t để gắn tag cho image, chính là version:

docker build -t abc:v2 . docker run -p 8000:80 -d --name NAME IMAGE-NAME:TAG

Push image to DockerHub

  • Đầu tiên cần tạo repo ta có repo-name
  • Để push được image lên DockerHub ta cần image đó phải có tên là username-of-DockerHub/Repo-name

docker tag image-name username-dockerhub / repo-name-on-docker-hub : version

➜ python-app-starting-setup ⚡                                                   17:17:13
▶ docker images
REPOSITORY   TAG       IMAGE ID       CREATED              SIZE
abc          v1        17b72ac3e71d   About a minute ago   1.02GB

➜ python-app-starting-setup ⚡                                                   17:17:58
▶ docker tag 17b72ac3e71d hjn4/udemy-docker-learn:v1

➜ python-app-starting-setup ⚡                                                   17:18:03
▶ docker images
REPOSITORY                TAG       IMAGE ID       CREATED              SIZE
hjn4/udemy-docker-learn   v1        17b72ac3e71d   About a minute ago   1.02GB
abc                       v1        17b72ac3e71d   About a minute ago   1.02GB

➜ python-app-starting-setup ⚡                                                   17:18:05
▶ docker push hjn4/udemy-docker-learn:v1
The push refers to repository [docker.io/hjn4/udemy-docker-learn]
eae17a074db1: Pushed
2b9b1a0059f9: Pushed
d08e8c3991bb: Mounted from library/python
00fdc842d356: Mounted from library/python
a2ad80a8ed2e: Mounted from library/python
74ec933aa24e: Mounted from library/python
d43f876e6f21: Mounted from library/python
9f843c569746: Mounted from library/python
bcd354c940e1: Mounted from library/python
1dae5147cd29: Mounted from library/python
v1: digest: sha256:167a2de6abd3d4b0b231e33431fb4f40f8f744e6132b228e730c2fe3d53bf46e size: 2420
  • Pull image from DockerHun

docker pull IMAGE:tag

Summary

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Cheat sheet

  • docker build . : Build a Dockerfile and create your own Image based on the file
    • -t NAME:TAG : Assign a NAME and a TAG to an image
  • docker run IMAGE_NAME : Create and start a new container based on image IMAGENAME (or use the image id)
    • --name NAME : Assign a NAME to the container. The name can be used for stopping and removing etc.
    • -d : Run the container in detached mode - i.e. output printed by the container is not visible, the command prompt / terminal does NOT wait for the container to stop
    • -it : Run the container in "interactive" mode - the container / application is then prepared to receive input via the command prompt / terminal. You can stop the container with CTRL + C when using the -it flag
    • --rm : Automatically remove the container when it's stopped
  • docker ps : List all running containers
    • -a : List all containers - including stopped ones
  • docker images : List all locally stored images
  • docker rm CONTAINER : Remove a container with name CONTAINER (you can also use the container id)
    • -f: Can remove when container is running
  • docker rmi IMAGE : Remove an image by name / id
  • docker container prune : Remove all stopped containers
  • docker image prune : Remove all dangling images (untagged images)
    • -a : Remove all locally stored images
  • docker push IMAGE : Push an image to DockerHub (or another registry) - the image name/ tag must include the repository name/ url
  • docker pull IMAGE : Pull (download) an image from DockerHub (or another registry) - this is done automatically if you just docker run IMAGE and the image wasn't pulled before