Redmineは結局、VPSに直接入れたが、試しに使ってみたい物などは、あまりサーバーの環境を汚さずに使いたいもの。

ということで、Docker環境を構築してみる。

1. Docker CEのインストール

dnf install -y yum-utils
yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
dnf -y install docker-ce docker-ce-cli containerd.io
systemctl start docker
systemctl enable docker
docker run hello-world 
Unable to find image 'hello-world:latest' locally
latest: Pulling from library/hello-world
0e03bdcc26d7: Pull complete
Digest: sha256:31b9c7d48790f0d8c50ab433d9c3b7e17666d6993084c002c2ff1ca09b96391d
Status: Downloaded newer image for hello-world:latest

Hello from Docker!
This message shows that your installation appears to be working correctly.

To generate this message, Docker took the following steps:
 1. The Docker client contacted the Docker daemon.
 2. The Docker daemon pulled the "hello-world" image from the Docker Hub.
    (amd64)
 3. The Docker daemon created a new container from that image which runs the
    executable that produces the output you are currently reading.
 4. The Docker daemon streamed that output to the Docker client, which sent it
    to your terminal.

To try something more ambitious, you can run an Ubuntu container with:
 $ docker run -it ubuntu bash

Share images, automate workflows, and more with a free Docker ID:
 https://hub.docker.com/

For more examples and ideas, visit:
 https://docs.docker.com/get-started/

2. Docker Composeのインストール

curl -L "https://github.com/docker/compose/releases/download/1.27.4/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose
chmod +x /usr/local/bin/docker-compose
ln -s /usr/local/bin/docker-compose /usr/bin/docker-compose
docker-compose --version
docker-compose version 1.27.4, build 40524192

3. 一般ユーザーでDockerを実行できるようにする

cat /etc/group | grep docker
docker:x:983:
gpasswd -a hoge docker    # hoge は一般ユーザー名
cat /etc/group | grep docker 
docker:x:983:hoge   # 追加されたのを確認

docker run hello-world
Hello from Docker!
This message shows that your installation appears to be working correctly.

To generate this message, Docker took the following steps:
 1. The Docker client contacted the Docker daemon.
 2. The Docker daemon pulled the "hello-world" image from the Docker Hub.
    (amd64)
 3. The Docker daemon created a new container from that image which runs the
    executable that produces the output you are currently reading.
 4. The Docker daemon streamed that output to the Docker client, which sent it
    to your terminal.

To try something more ambitious, you can run an Ubuntu container with:
 $ docker run -it ubuntu bash

Share images, automate workflows, and more with a free Docker ID:
 https://hub.docker.com/

For more examples and ideas, visit:
 https://docs.docker.com/get-started/

一般ユーザーのまま、docker run コマンドが使えるようになった。

4. Docker + Docker Composeの動作確認

下記URLで、確認用のサンプルが紹介されているので、それを試してみる。

https://docs.docker.com/compose/gettingstarted/

4.1. テストプログラムの準備

mkdir ~/composetest
cd ~/composetest
vi app.py 

 import time

import redis
from flask import Flask

app = Flask(__name__)
cache = redis.Redis(host='redis', port=6379)

def get_hit_count():
    retries = 5
    while True:
        try:
            return cache.incr('hits')
        except redis.exceptions.ConnectionError as exc:
            if retries == 0:
                raise exc
            retries -= 1
            time.sleep(0.5)

@app.route('/')
def hello():
    count = get_hit_count()
    return 'Hello World! I have been seen {} times.\n'.format(count)

vi requirements.txt

flask
redis

4.2. Dockerfile

vi Dockerfile 

FROM python:3.7-alpine
WORKDIR /code
ENV FLASK_APP=app.py
ENV FLASK_RUN_HOST=0.0.0.0
RUN apk add --no-cache gcc musl-dev linux-headers
COPY requirements.txt requirements.txt
RUN pip install -r requirements.txt
EXPOSE 5000
COPY . .
CMD ["flask", "run"]

4.3. docker-compose.yml

vi docker-compose.yml 

version: "3.9"
services:
  web:
    build: .
    ports:
      - "5000:5000"
  redis:
    image: "redis:alpine"

4.4. ビルド＆起動

docker-compose up
Creating network "composetest_default" with the default driver
Building web
Step 1/10 : FROM python:3.7-alpine
3.7-alpine: Pulling from library/python
（略）
web_1    |  * Running on http://0.0.0.0:5000/ (Press CTRL+C to quit)

コンテナが一通り起動し終わったら、ブラウザから下記にアクセス。

http://[VPSのグローバルIP]:5000/

“Hello World! I have been seen xx times.”というテキストがWebページ状に表示されたら、疎通確認OK。