CentOS7にDocker入れてコンテナを動かす

# Docker ホストを作る

Docker入門1日目のメモ。
インストールしたてのCentOS7にDockerをインストールして、イメージ作って、コンテナ作るまでを書いておく。

## 構成

* CentOS7

## ネットワーク構成

```
  Internet
    |
  router(nat)
    |
  --o-----o-----o-- 10.0.2.0/24
          |     |
        dhcp    | .15
              enp0s3
              centos7
              enp0s8
                | .101
                |
              --o-----o-----o--- 192.168.99.0/24
                      |     |
                    dhcp  windows
```

## ハードウェア構成

* centos7
  * Mem: 1024MB
  * CPU: 1
  * Disk: 8GB

## 手順

### Dockerをインストールする

CentOS7 を最小構成でインストールする。

コンソールで操作する。

```bash
nmcli c up enp0s8
hostname -I
  # --> 192.168.99.101
hostnamectl set-hostname centos7
```

windowsからSSHで操作する。

```powershell
ssh root@192.168.99.101
nmcli c modify enp0s8 connection.autoconnect yes
nmcli c modify enp0s3 connection.autoconnect yes
yum update -y

yum install yum-utils -y
needs-restarting
systemctl reboot

ping -t 192.168.99.101
ssh root@192.168.99.101

yum install -y yum-utils device-mapper-persistent-data lvm2

yum-config-manager \
--add-repo https://download.docker.com/linux/centos/docker-ce.repo

yum install docker-ce docker-ce-cli containerd.io -y

systemctl enable docker
systemctl start docker

docker run hello-world
```

ログ

```console
# docker run hello-world
Unable to find image 'hello-world:latest' locally
latest: Pulling from library/hello-world
1b930d010525: Pull complete
Digest: sha256:2557e3c07ed1e38f26e389462d03ed943586f744621577a99efb77324b0fe535
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/
```

### docker コマンドの機能一覧を得る

```console
# docker

Usage:  docker [OPTIONS] COMMAND

A self-sufficient runtime for containers

Options:
      --config string      Location of client config files
                           (default "/root/.docker")
  -D, --debug              Enable debug mode
  -H, --host list          Daemon socket(s) to connect to
  -l, --log-level string   Set the logging level
                           ("debug"|"info"|"warn"|"error"|"fatal") (default "info")
      --tls                Use TLS; implied by --tlsverify
      --tlscacert string   Trust certs signed only by this CA
                           (default "/root/.docker/ca.pem")
      --tlscert string     Path to TLS certificate file (default
                           "/root/.docker/cert.pem")
      --tlskey string      Path to TLS key file (default
                           "/root/.docker/key.pem")
      --tlsverify          Use TLS and verify the remote
  -v, --version            Print version information and quit

Management Commands:
  builder     Manage builds
  config      Manage Docker configs
  container   Manage containers
  engine      Manage the docker engine
  image       Manage images
  network     Manage networks
  node        Manage Swarm nodes
  plugin      Manage plugins
  secret      Manage Docker secrets
  service     Manage services
  stack       Manage Docker stacks
  swarm       Manage Swarm
  system      Manage Docker
  trust       Manage trust on Docker images
  volume      Manage volumes

Commands:
  attach      Attach local standard input, output, and error streams to a running container
  build       Build an image from a Dockerfile
  commit      Create a new image from a container's changes
  cp          Copy files/folders between a container and the local filesystem
  create      Create a new container
  diff        Inspect changes to files or directories on a container's filesystem
  events      Get real time events from the server
  exec        Run a command in a running container
  export      Export a container's filesystem as a tar archive
  history     Show the history of an image
  images      List images
  import      Import the contents from a tarball to create a filesystem image
  info        Display system-wide information
  inspect     Return low-level information on Docker objects
  kill        Kill one or more running containers
  load        Load an image from a tar archive or STDIN
  login       Log in to a Docker registry
  logout      Log out from a Docker registry
  logs        Fetch the logs of a container
  pause       Pause all processes within one or more containers
  port        List port mappings or a specific mapping for the container
  ps          List containers
  pull        Pull an image or a repository from a registry
  push        Push an image or a repository to a registry
  rename      Rename a container
  restart     Restart one or more containers
  rm          Remove one or more containers
  rmi         Remove one or more images
  run         Run a command in a new container
  save        Save one or more images to a tar archive (streamed to STDOUT by default)
  search      Search the Docker Hub for images
  start       Start one or more stopped containers
  stats       Display a live stream of container(s) resource usage statistics
  stop        Stop one or more running containers
  tag         Create a tag TARGET_IMAGE that refers to SOURCE_IMAGE
  top         Display the running processes of a container
  unpause     Unpause all processes within one or more containers
  update      Update configuration of one or more containers
  version     Show the Docker version information
  wait        Block until one or more containers stop, then print their exit codes

Run 'docker COMMAND --help' for more information on a command.
```

### イメージからコンテナを作ってシェルを使う

centosがなければ、ダウンロードする。
centosはDocker公式イメージの１つ。

```bash
docker run -it centos bash
```

exit で終了する

### centosイメージで SELinux が有効か調べる

```bash
docker run -it centos bash
yum provides '*bin/getenforce'
yum install libselinux-utils -y
getenforce
  # --> Disabled
```

### イメージの一覧を得る

```bash
docker image ls
```

### イメージを作る

#### 標準出力に出力するイメージを作る

```bash
mkdir -pv $HOME/dir1
cd $HOME/dir1
cat <<'__DOCKERFILE__' | tee $HOME/dir1/Dockerfile >/dev/null
FROM centos
MAINTAINER kumarstack55 <kumarstack55@gmail.com>
CMD echo a
__DOCKERFILE__
docker build --tag=tag1 .
docker image ls

# 実行してみる
docker run tag1
  # --> a
```

#### httpd をサービスするイメージを作る

```bash
mkdir -pv $HOME/dir2
cd $HOME/dir2
cat <<'__DOCKERFILE__' | tee $HOME/dir2/Dockerfile >/dev/null
FROM centos
MAINTAINER kumarstack55 <kumarstack55@gmail.com>
RUN yum install httpd -y
RUN echo 'ServerName localhost:80' >/etc/httpd/conf.d/servername.conf
RUN echo '<html><body>a</body></html>' >/var/www/html/index.html
EXPOSE 80
CMD /usr/sbin/httpd -D FOREGROUND
__DOCKERFILE__
docker build --tag=tag2 .
docker image ls
```

実行してみる

```
docker run -d -p 10080:80 tag2
```

windows で次のURLを見る。

```
http://192.168.99.101:10080/
  # --> a
```

centos7 で docker コンテナを止める。

ここでは filter で指定タグを探しているが、
ancestor は範囲に子を含むので、微妙。
もっといい方法がありそう。

```bash
docker ps
docker ps --filter ancestor=tag2 --format "{{.ID}}"
docker stop $(docker ps --filter ancestor=tag2 --format "{{.ID}}")
```

### イメージからコンテナを作る

再掲。

```bash
docker run centos7
docker run centos7 -it bash
```

```bash
docker run tag1
```

```bash
docker run -d -p 10080:80 tag2
```

### コンテナの一覧を得る

```bash
docker ps
docker ps -a
```

### コンテナを消す

tag2のコンテナを消す。

```bash
docker ps --all
docker ps --all --filter ancestor=tag2 --format "{{.ID}}"
docker rm $(docker ps --all --filter ancestor=tag2 --format "{{.ID}}")
```

### イメージを消す

tag1のコンテナを消す。
force で紐づくコンテナもまとめて消してくれる。
事前に docker rm すれば force は不要となる。

```bash
docker image ls
docker images tag1 --format "{{.ID}}"
docker rmi $(docker images tag1 --format "{{.ID}}")
docker rmi --force $(docker images tag1 --format "{{.ID}}")
```

## 参考資料

Get started with Docker
https://docs.docker.com/get-started/

https://docs.docker.com/install/

https://docs.docker.com/docker-hub/official_images/

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