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[Appendix A] - Basics of Docker

Section 1: Dive Into Docker!

520. What is Docker?

  • Docker Client (Docker CLI): Tool that we are going to issue commands to
  • Docker Server (Docker Deamon): Tool that is responsible for creating images, running, containers, etc
  • Docker Machine
  • Docker Image
  • Docker Container
  • Docker Hub
  • Docker Compose

528. Using the Docker Client

docker version
docker run hello-world

529. But Really... What's a Container?

  • Kernel: opens endpoints to allocate hardware resources such as HD, memory and network
  • Namespacing: Isolating resources per process (or group of processes)
  • Control Groups(cgroups): Limit amount of resources used per process

namespacing and cgroups belong to linux system

530. How's Docker Running on Your Computer?

Docker Server is based on linux virtual machine
So it would have several containers and they communicate via Linux Kernel

Section 2: Manipulating Containers with the Docker Client

531. Docker Run in Detail

docker run hello-world

532. Overriding Default Commands

docker run busybox echo hi there
docker run busybox ls
docker run busybox ls bin

why busybox, not hello-world?
-> hello-world doesn't contain all of them, but only one single file for hello-world

533. Listing Running Containers : docker ps

docker ps
docker run busybox ping google.com
docker ps
docker ps --all

534. Container Lifecycle

docker run = docker create + docker start

docker create hello-world
# 345e9a72706489ad455541d2d2c55991d28f85b63233a847dee307fec4e3a9be
docker start -a 345e9a72706489ad455541d2d2c55991d28f85b63233a847dee307fec4e3a9be

535. Restarting Stopped Containers

docker ps -a
# | CONTAINER ID |  IMAGE  | COMMAND  |    CREATED     |          STATUS           |     PORTS      | NAMES |
# | :----------: | :-----: | :------: | :------------: | :-----------------------: | :------------: | :---: |
# | 71e182459e15 | busybox | "ls bin" | 13 minutes ago | Exited (0) 33 seconds ago | stoic_meninsky |       |
docker start -a 71e182459e15
docker start -a stoic_meninsky

536. Removing Stopped Containers

docker system prune
# WARNING! This will remove:
#   - all stopped containers
#   - all networks not used by at least one container
#   - all dangling images
#   - all dangling build cache

docker container prune

537. Retrieving Output Logs

docker create busybox echo hi there
# 5307aeeb3432e854ed7eb2a6884e4336cb71bea8be64e50076f8870beb7c5e35
docker ps -a
# | CONTAINER ID |  IMAGE  |     COMMAND     |    CREATED     | STATUS  | PORTS |     NAMES     |
# | :----------: | :-----: | :-------------: | :------------: | :-----: | :---: | :-----------: |
# | 5307aeeb3432 | busybox | "echo hi there" | 28 seconds ago | Created |       | peaceful_benz |
docker start 5307aeeb3432e854ed7eb2a6884e4336cb71bea8be64e50076f8870beb7c5e35
docker container ls -a
# | CONTAINER ID |  IMAGE  |     COMMAND     |    CREATED     |          STATUS          | PORTS |     NAMES     |
# | :----------: | :-----: | :-------------: | :------------: | :----------------------: | :---: | :-----------: |
# | 5307aeeb3432 | busybox | "echo hi there" | 53 seconds ago | Exited (0) 2 seconds ago |       | peaceful_benz |
docker logs 5307aeeb3432
# hi there

538. Stopping Containers

docker create busybox ping google.com
# 0547fcddf48255831fc4695fba2c49426237b229746edb94fb4c7620ef186bcf
docker start 0547fcddf48255831fc4695fba2c49426237b229746edb94fb4c7620ef186bcf
docker logs 0547fcddf48255831fc4695fba2c49426237b229746edb94fb4c7620ef186bcf
docker ps
  • Stop a Container: docker stop <container id>
    • stop -> SIGTERM -> give a little bit of time to shut it down and clean up
    • The SIGTERM signal is a generic signal used to cause program termination. Unlike SIGKILL, this signal can be blocked, handled, and ignored. It is the normal way to politely ask a program to terminate.
    • with docker stop command, if the container is not automatically stopped in 10 seconds, docker kill will be executed.
  • Kill a Container: docker kill <container id>
    • kill -> SIGKILL -> shutdown immediately
    • The SIGKILL signal is used to cause immediate program termination. It cannot be handled or ignored, and is therefore always fatal. It is also not possible to block this signal.

Termination Signals (The GNU C Library)

docker stop 0547fcddf482
# ping command doesn't really react to stop(SIGTERM) command
# so kill will be executed
docker start 0547fcddf482
docker kill 0547fcddf482

539. Multi-Command Containers

# already installed redis via brew
redis-server
redis-cli
set mynumber 5
get mynumber
# 5
docker run redis

540. Executing Commands in Running Containers

docker exec -it <container id> <command>
docker run redis
docker ps
docker exec -it 73b7e60d4626 redis-cli
# [127.0.0.1:6379>

541. The Purpose of the 'it' Flag

  • STDIN
  • STDOUT
  • STDERR
-i, --interactive          Keep STDIN open even if not attached
    --privileged           Give extended privileges to the command
-t, --tty                  Allocate a pseudo-TTY
docker exec -i 73b7e60d4626 redis-cli
# it's attached but it doens't have pretty/helping terminal support

542. Getting a Command Prompt in a Container

docker exec -it 73b7e60d4626 sh
cd /
ls
# bin  boot  data  dev  etc  home  lib  lib64  media  mnt  opt  proc  root  run  sbin  srv  sys  tmp  usr  var
echo hi there
# hi there
export b=5
echo $b
redis-cli
# [127.0.0.1:6379>
Ctrl + D (to exit)
  • bash
  • powershell
  • zsh
  • sh

Traditionally most containers have sh included, but some have bash

543. Starting with a Shell

docker run -it busybox sh
ping google.com

544. Container Isolation

docker run -it busybox sh
# In a new tab
docker run -it busybox sh
touch hithere
ls

If I run two containers and I create a new file on one, basically they don't share file system.

Section 3: Building Custom Images Through Docker Server

546. Buildkit for Docker Desktop v2.4.0+ and Edge

547. Building a Dockerfile

# 24-docker/01-redis-image
docker build .
docker run 62d17fb20f2136049f12adbefc57552b347a96849cd918d4e7b78ec9bfcca00d

548. Dockerfile Teardown

# Use an existing docker image as a base
FROM alpine

# Download and install a dependency
RUN apk add --update redis

# Tell the image what to do when it starts as a container
CMD ["redis-server"]
  • alpine: A minimal Docker image based on Alpine Linux with a complete package index and only 5 MB in size
  • apk: Alpine Linux package manager

550. The Build Process in Detail

  1. docker build .: give me docker image out of docker cli

the build result between option "buildkit": true and "buildkit": false are different.

# "buildkit": true
noah@Noahs-MacBook-Pro 01-redis-image % docker build .
[+] Building 13.2s (7/7) FINISHED
 => [internal] load build definition from Dockerfile                                                                            0.1s
 => => transferring dockerfile: 240B                                                                                            0.0s
 => [internal] load .dockerignore                                                                                               0.0s
 => => transferring context: 2B                                                                                                 0.0s
 => [internal] load metadata for docker.io/library/alpine:latest                                                                7.4s
 => [auth] library/alpine:pull token for registry-1.docker.io                                                                   0.0s
 => [1/2] FROM docker.io/library/alpine@sha256:21a3deaa0d32a8057914f36584b5288d2e5ecc984380bc0118285c70fa8c9300                 1.2s
 => => resolve docker.io/library/alpine@sha256:21a3deaa0d32a8057914f36584b5288d2e5ecc984380bc0118285c70fa8c9300                 0.0s
 => => sha256:59bf1c3509f33515622619af21ed55bbe26d24913cedbca106468a5fb37a50c3 2.82MB / 2.82MB                                  0.8s
 => => sha256:21a3deaa0d32a8057914f36584b5288d2e5ecc984380bc0118285c70fa8c9300 1.64kB / 1.64kB                                  0.0s
 => => sha256:e7d88de73db3d3fd9b2d63aa7f447a10fd0220b7cbf39803c803f2af9ba256b3 528B / 528B                                      0.0s
 => => sha256:c059bfaa849c4d8e4aecaeb3a10c2d9b3d85f5165c66ad3a4d937758128c4d18 1.47kB / 1.47kB                                  0.0s
 => => extracting sha256:59bf1c3509f33515622619af21ed55bbe26d24913cedbca106468a5fb37a50c3                                       0.3s
 => [2/2] RUN apk add --update redis                                                                                            3.7s
 => exporting to image                                                                                                          0.5s
 => => exporting layers                                                                                                         0.5s
 => => writing image sha256:62d17fb20f2136049f12adbefc57552b347a96849cd918d4e7b78ec9bfcca00d                                    0.0s
# "buildkit": false
noah@Noahs-MacBook-Pro 01-redis-image % docker build .
Sending build context to Docker daemon  2.048kB
Step 1/3 : FROM alpine
latest: Pulling from library/alpine
59bf1c3509f3: Already exists
Digest: sha256:21a3deaa0d32a8057914f36584b5288d2e5ecc984380bc0118285c70fa8c9300
Status: Downloaded newer image for alpine:latest
 ---> c059bfaa849c
Step 2/3 : RUN apk add --update redis
 ---> Running in 041ffef007ff
fetch https://dl-cdn.alpinelinux.org/alpine/v3.15/main/x86_64/APKINDEX.tar.gz
fetch https://dl-cdn.alpinelinux.org/alpine/v3.15/community/x86_64/APKINDEX.tar.gz
(1/1) Installing redis (6.2.6-r0)
Executing redis-6.2.6-r0.pre-install
Executing redis-6.2.6-r0.post-install
Executing busybox-1.34.1-r3.trigger
OK: 8 MiB in 15 packages
Removing intermediate container 041ffef007ff
 ---> 505677ae7f28
Step 3/3 : CMD ["redis-server"]
 ---> Running in 59d6409a9a32
Removing intermediate container 59d6409a9a32
 ---> bc5303779113
Successfully built bc5303779113
  • Each step except step 1, follows this process
    1. Create a new temporary container based on an image from the previous step
    2. Execute command
    3. Remove the temporary container
    4. Create a new image based on the result

552. Rebuilds with Cache

RUN apk add --update gcc

noah@Noahs-MacBook-Pro 01-redis-image % docker build .
Sending build context to Docker daemon  2.048kB
Step 1/4 : FROM alpine
 ---> c059bfaa849c
Step 2/4 : RUN apk add --update redis
 ---> Using cache
 ---> 505677ae7f28
Step 3/4 : RUN apk add --update gcc
 ---> Running in 4063e9253202
fetch https://dl-cdn.alpinelinux.org/alpine/v3.15/main/x86_64/APKINDEX.tar.gz
fetch https://dl-cdn.alpinelinux.org/alpine/v3.15/community/x86_64/APKINDEX.tar.gz
(1/11) Installing libgcc (10.3.1_git20211027-r0)
(2/11) Installing libstdc++ (10.3.1_git20211027-r0)
(3/11) Installing binutils (2.37-r3)
(4/11) Installing libgomp (10.3.1_git20211027-r0)
(5/11) Installing libatomic (10.3.1_git20211027-r0)
(6/11) Installing libgphobos (10.3.1_git20211027-r0)
(7/11) Installing gmp (6.2.1-r0)
(8/11) Installing isl22 (0.22-r0)
(9/11) Installing mpfr4 (4.1.0-r0)
(10/11) Installing mpc1 (1.2.1-r0)
(11/11) Installing gcc (10.3.1_git20211027-r0)
Executing busybox-1.34.1-r3.trigger
OK: 118 MiB in 26 packages
Removing intermediate container 4063e9253202
 ---> 83fc43ba34a6
Step 4/4 : CMD ["redis-server"]
 ---> Running in e36ad7baea5f
Removing intermediate container e36ad7baea5f
 ---> 44f7d19aff95
Successfully built 44f7d19aff95
RUN apk add --update redis
RUN apk add --update gcc
⬇️
RUN apk add --update gcc
RUN apk add --update redis

if the series of order changes, we cannot use cache and it will build all again

553. Tagging an Image

docker build -t pcsmomo/redis:latest .

  • pcsmomo/redis:latest
    • pcsmomo: my docker id
    • redis: repo/project name
    • latest: version
docker build -t pcsmomo/redis:latest .
docker run pcsmomo/redis

555. Manual Image Generation with Docker Commit

Just for Practice Manual Image generation

docker run -it alpine sh
apk add --update redis
# new tab
docker ps
# | CONTAINER ID |  IMAGE  |     COMMAND     |      CREATED       |          STATUS          | PORTS |     NAMES     |
# | :----------: | :-----: | :-------------: | :----------------: | :----------------------: | :---: | :-----------: |
# | 5f943d0f3d3a | alpine  |      "sh"       | About a minute ago |    Up About a minute     |       | sweet_pascal  |
docker commit -c 'CMD ["redis-server"]' 5f943d0f3d3a
# sha256:c01e6d5982bc36560e9d6e65d6cf5ca1758418e06a04eb7b343b899a4fd9d178
docker run c01e6d5982bc3

we don't have to copy all the full sha256 strings. Just unique enough is fine

Section 4: Making Real Projects with Docker

557. Node Server Setup

mkdir 02-simpleweb
cd 02-simpleweb
touch package.json

558. A Few Planned Errors

docker build .
# /bin/sh: npm: not found

560. Base Imagee Issues

  • node:alpine
    • alpine : small and compact version
docker build .
# npm ERR! Tracker "idealTree" already exists

562. Copying Build Files

copy source dest (source: my side side first)

copy ./ ./

docker build -t pcsmomo/simpleweb .
docker run pcsmomo/simpleweb
# navigate localhost:8080 -> This site can’t be reached

564. Container Port Forwarding

docker run -p 8080:8080 pcsmomo/simpleweb
# 8080:8080, first my side:container side later
docker run -p 5000:8080 pcsmomo/simpleweb

565. Specifying a Working Directory

  • WORKDIR /usr/app
    • if not specifying this, it will do all the instructions such as copy/install on the 'root' directory
# working on shell when running
docker run -it pcsmomo/simpleweb sh
# "exec", working on shell if the app is running
docker run -p 8080:8080 pcsmomo/simpleweb
docker ps
docker exec -it 81f2ed1aebd7 sh

567. Minimizing Cache Busting and Rebuilds

# Install some dependencies
COPY ./package.json ./
RUN npm install
COPY ./ ./