Docker Quick Start Guide and Frontend Project Containerization

Docker Quick Start

1.1 Install Docker (Linux)

Yum repository: https://mirrors.tuna.tsinghua.edu.cn/docker-ce/linux/centos/docker-ce.repo (replace the URL in the repo file for faster download).

:%s/download.docker.com/mirrors.tuna.tsinghua.edu.cn\/docker-ce/g

Docker version 19.03.12, build 48a66213fe

dnf config-manager --add-repo=https://download.docker.com/linux/centos/docker-ce.repo

dnf list docker-ce

dnf install docker-ce --nobest -y

systemctl start docker
systemctl enable docker

docker -v

1.2 Docker Commands

info – display system information

# docker info
Client:
  Debug Mode: false

Server:
  Containers: 0
  Running: 0
  Paused: 0
  Stopped: 0
  Images: 0
  Server Version: 18.09.1
  Storage Driver: overlay2
  Backing Filesystem: xfs
  Supports d_type: true
  Native Overlay Diff: true
  Logging Driver: json-file
  Cgroup Driver: cgroupfs

version – show Docker version information

# docker version
Client: Docker Engine - Community
 Version:           19.03.12
 API version:       1.39
 Go version:        go1.13.10
 Git commit:        48a66213fe
 Built:             Mon Jun 22 15:46:54 2020
 OS/Arch:           linux/amd64
 Experimental:      false

Server: Docker Engine - Community
 Engine:
  Version:          18.09.1
  API version:      1.39 (minimum version 1.12)
  Go version:       go1.10.6
  Git commit:       4c52b90
  Built:            Wed Jan  9 19:06:30 2019
  OS/Arch:          linux/amd64
  Experimental:     false

Container Lifecycle

search – find images docker search hello-world pull – download an image from Docker Hub

# docker pull hello-world
Using default tag: latest
... (output omitted for brevity)

images – list local images

# docker images
REPOSITORY   TAG       IMAGE ID       CREATED        SIZE
hello-world  latest    bf756fb1ae65   6 months ago   13.3kB

run – start a container

-i : interactive mode

-t : allocate a pseudo‑TTY

-d : run in background

--name : assign a name to the container

-p : port binding

docker run [options] IMAGE

docker run hello-world

docker run --name mywebserver -it nginx

# docker run --name mywebserver -itd nginx
... (container ID output)

ps – list container processes (add -a to show all)

# docker ps
CONTAINER ID   IMAGE   COMMAND   CREATED   STATUS   PORTS   NAMES

# docker ps -a
... (output showing stopped containers)

rm – remove a container (use -f to force)

# docker rm mywebserver
mywebserver

# docker rm 01bdedde3725
01bdedde3725

start / restart / stop – control container state

# docker stop mywebserver
mywebserver
# docker start mywebserver
mywebserver
# docker restart mywebserver
mywebserver

stats – display resource usage

# docker stats mywebserver
CONTAINER ID   NAME          CPU %   MEM USAGE / LIMIT   MEM %   NET I/O   BLOCK I/O   PIDS
8d485b358cc6   mywebserver   0.00%   2.309MiB / 3.664GiB   0.06%   3.44kB / 0B   0B / 0B   2

logs – view container logs (add -f for live streaming)

# docker logs -f mywebserver
... (log output)

pause / unpause – suspend and resume a container

# docker pause mywebserver
mywebserver
# docker unpause mywebserver
mywebserver

rename – rename a container

# docker rename mywebserver webserver
# docker ps
... (container now named webserver)

inspect – show detailed container information (JSON output omitted for brevity)

# docker inspect webserver
[ { "Id": "8d485b...", "Created": "2020-07-09T01:55:08.20199984Z", ... } ]

kill – terminate a container process

# docker kill webserver
webserver

top – view processes inside a container

# docker top webserver
UID   PID   PPID   C   STIME   TTY   TIME   CMD
root  7153  7136  0   22:30   pts/0 00:00:00 nginx: master process nginx -g daemon off;

exec – run a command inside a running container

# docker exec -it webserver bash
root@8d485b...:/# ls

port – display port bindings

# docker port webserver
80/tcp -> 0.0.0.0:8000

cp – copy files between host and container

# docker cp /etc/hosts webserver:/tmp
# docker exec -it webserver ls /tmp
hosts
# docker cp webserver:/tmp/hosts ./

diff – show filesystem changes in a container

# docker diff webserver
C /etc
C /etc/nginx
... (list omitted)

export / import – export a container's filesystem to a tar archive and import it as an image

# docker export -o test.tar webserver
# mkdir docker && mv test.tar docker/
# cd docker && tar xf test.tar
... (files listed)

Image Operations

history – view image build history

# docker history nginx
IMAGE        CREATED      CREATED BY                                 SIZE   COMMENT
2622e6cca7eb 4 weeks ago  /bin/sh -c #(nop)  CMD ["nginx" "-g" ...]   0B
... (output truncated)

login / logout – authenticate with Docker Hub

# docker login
Username: devopsvip
Password: ********
Login Succeeded

# docker logout
Removing login credentials for https://index.docker.io/v1/

search / pull / images / tag / push / rmi – typical image workflow (examples shown for hello‑world and a custom image)

# docker search hello-world
# docker pull hello-world
# docker images
# docker tag hello-world devopsvip/docker:latest
# docker push devopsvip/docker:latest
# docker rmi devopsvip/docker:latest

commit – create a new image from a container's changes

# docker commit -a "devopsvipxx" -m "hhahh" webserver webserver:v1
sha256:d315f2bb4060

build – build an image from a Dockerfile

# docker build .
# docker build -t webserver:v2 .
Successfully built d315f2bb4060
Successfully tagged webserver:v2

load / save – load an image from a tar archive or save an image to a tar archive

# docker save -o webserver-v2.tar webserver:v2
# docker load -i webserver-v2.tar
Loaded image: webserver:v2

create / update – create a stopped container and update its resources

# docker create --name webnewserver nginx
bbc81d2c7283
# docker start webnewserver
webnewserver
# docker update --memory 1G --memory-swap 1G webnewserver

Frontend Project Containerization

1.1 Manual Deployment of Frontend Project

Install npm (CentOS 8 may prompt for installation) or manually install Node.js.

git clone https://github.com/dockersamples/node-bulletin-board
cd node-bulletin-board/bulletin-board-app
npm install
npm start
# Application runs on port 8080

Access: http://192.168.1.105:8080/#

1.2 Deploy with Docker

Create a Dockerfile

FROM node:current-slim   # base image
WORKDIR /usr/src/app      # set working directory
COPY package.json .       # copy package.json
RUN npm install          # install dependencies
EXPOSE 8080               # expose port
CMD ["npm", "start"]    # start the app
COPY . .                  # copy source code

Build the image

docker build -t bulletinboard:1.0 .

Run a container

# docker run -itd --name bb -p 8000:8080 bulletinboard:1.0

Access the service on host port 8000.

Remove the container and image

docker stop bb
docker rm bb
docker rmi bulletinboard:1.0

1.3 Push Image to Registry

Tag and push the image to Docker Hub (repository name: bulletinboard)

# docker tag bulletinboard:1.0 devopsvip/bulletinboard:1.0
# docker push devopsvip/bulletinboard:1.0

FAQ

Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?

Got permission denied while trying to connect to the Docker daemon socket ...
## Solution
# usermod -aG docker usera
# su - usera
# docker images

docker: Error response from daemon: Conflict. The container name "/mywebserver" is already in use ...
## Solution
1. Use a different name: docker run --name mywebserver01 -it nginx
2. Remove the existing container: docker rm mywebserver

Error response from daemon: Container 8d485b... is not running
## Solution
Start the container again before executing commands.

How to expose nginx externally? Use -p host_port:container_port when running.

# docker run --name webserver -p 8000:80 -itd nginx
# curl 127.0.0.1:8000
... (HTML page output)

How to register a Docker Hub account? (Screenshots omitted)

denied: requested access to the resource is denied
## Solution
docker login

How to copy a local image to a remote machine?

# docker save -o webserver-v2.tar webserver:v2
# scp webserver-v2.tar [email protected]:/tmp/
# ssh [email protected]
# docker load -i /tmp/webserver-v2.tar

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