Podman を使ってコンテナを起動してみた (その1)

◆ Live配信スケジュール ◆
サイオステクノロジーでは、Microsoft MVPの武井による「わかりみの深いシリーズ」など、定期的なLive配信を行っています。
⇒ 詳細スケジュールはこちらから
⇒ 見逃してしまった方はYoutubeチャンネルをご覧ください

【5/21開催】Azure OpenAI ServiceによるRAG実装ガイドを公開しました
生成AIを活用したユースケースで最も一番熱いと言われているRAGの実装ガイドを公開しました。そのガイドの紹介をおこなうイベントです!!
https://tech-lab.connpass.com/event/315703/

こんにちは。サイオステクノロジー OSS サポート担当 Y です。

今回は、Podman の検証実施してみました。(※以下の内容は CentOS 7.6/Podman 1.3.2 にて検証しています。)

1 ■はじめに
2 ■Podman のインストール (CentOS)
3 ■動作検証
4 ■まとめ

■はじめに

先日リリースされた Red Hat Enterprise Linux 8 では、コンテナ管理ツールとして Docker ではなく Podman が同梱されています。今回は、この Podman を試してみました。

■Podman のインストール (CentOS)

今回は CentOS 7.6 で検証を行うため、まずは Podman をインストールします。

以下の通り、extras リポジトリにパッケージが用意されているため、yum でインストールします。

[root@podman-test ~]# yum list podman
Loaded plugins: fastestmirror, langpacks
Loading mirror speeds from cached hostfile
 * base: ftp.iij.ad.jp
 * extras: ftp.iij.ad.jp
 * updates: ftp.iij.ad.jp
Available Packages
podman.x86_64             1.3.2-1.git14fdcd0.el7.centos              extras
[root@podman-test ~]#

[root@podman-test ~]# yum install -y podman
Loaded plugins: fastestmirror, langpacks
Loading mirror speeds from cached hostfile
 * base: ftp.iij.ad.jp
 * extras: ftp.iij.ad.jp
 * updates: ftp.iij.ad.jp
Resolving Dependencies
--> Running transaction check
---> Package podman.x86_64 0:1.3.2-1.git14fdcd0.el7.centos will be installed

～(中略)～

Installed:
  podman.x86_64 0:1.3.2-1.git14fdcd0.el7.centos                            

Dependency Installed:
  atomic-registries.x86_64 1:1.22.1-26.gitb507039.el7.centos               
  container-selinux.noarch 2:2.99-1.el7_6                                  
  containernetworking-plugins.x86_64 0:0.7.5-2.el7.centos                  
  containers-common.x86_64 1:0.1.35-2.git404c5bd.el7.centos                
  criu.x86_64 0:3.9-5.el7                                                  
  libnet.x86_64 0:1.1.6-7.el7                                              
  protobuf-c.x86_64 0:1.0.2-3.el7                                          
  python-pytoml.noarch 0:0.1.14-1.git7dea353.el7                           
  runc.x86_64 0:1.0.0-59.dev.git2abd837.el7.centos                         

Complete!
[root@podman-test ~]#

[root@podman-test ~]# podman version
Version:            1.3.2
RemoteAPI Version:  1
Go Version:         go1.10.3
OS/Arch:            linux/amd64
[root@podman-test ~]#

以上でインストールは完了です。

■動作検証

では、さっそく Podman を使ってコンテナを起動してみます。

以下の様に、podman コマンドには様々なサブコマンドが用意されていますが、見たところ docker コマンドとほぼ同じ雰囲気で使えそうです。

[root@podman-test ~]# podman help
manage pods and images

Usage:
  podman [flags]
  podman [command]

Available Commands:
  attach      Attach to a running container
  build       Build an image using instructions from Dockerfiles
  commit      Create new image based on the changed container
  container   Manage Containers
  cp          Copy files/folders between a container and the local filesystem
  create      Create but do not start a container
  diff        Inspect changes on container's file systems
  events      Show podman events
  exec        Run a process in a running container
  export      Export container's filesystem contents as a tar archive
  generate    Generated structured data
  healthcheck Manage Healthcheck
  help        Help about any command
  history     Show history of a specified image
  image       Manage images
  images      List images in local storage
  import      Import a tarball to create a filesystem image
  info        Display podman system information
  init        Initialize one or more containers
  inspect     Display the configuration of a container or image
  kill        Kill one or more running containers with a specific signal
  load        Load an image from container archive
  login       Login to a container registry
  logout      Logout of a container registry
  logs        Fetch the logs of a container
  mount       Mount a working container's root filesystem
  pause       Pause all the processes in one or more containers
  play        Play a pod
  pod         Manage pods
  port        List port mappings or a specific mapping for the container
  ps          List containers
  pull        Pull an image from a registry
  push        Push an image to a specified destination
  restart     Restart one or more containers
  rm          Remove one or more containers
  rmi         Removes one or more images from local storage
  run         Run a command in a new container
  save        Save image to an archive
  search      Search registry for image
  start       Start one or more containers
  stats       Display a live stream of container resource usage statistics
  stop        Stop one or more containers
  system      Manage podman
  tag         Add an additional name to a local image
  top         Display the running processes of a container
  umount      Unmounts working container's root filesystem
  unpause     Unpause the processes in one or more containers
  unshare     Run a command in a modified user namespace
  version     Display the Podman Version Information
  volume      Manage volumes
  wait        Block on one or more containers

Flags:
      --cgroup-manager string        Cgroup manager to use (cgroupfs or systemd, default systemd)
      --cni-config-dir string        Path of the configuration directory for CNI networks
      --config string                Path of a libpod config file detailing container server configuration options
      --conmon string                Path of the conmon binary
      --cpu-profile string           Path for the cpu profiling results
      --default-mounts-file string   Path to default mounts file
      --help                         Help for podman
      --hooks-dir strings            Set the OCI hooks directory path (may be set multiple times)
      --log-level string             Log messages above specified level: debug, info, warn, error, fatal or panic (default "error")
      --namespace string             Set the libpod namespace, used to create separate views of the containers and pods on the system
      --network-cmd-path string      Path to the command for configuring the network
      --root string                  Path to the root directory in which data, including images, is stored
      --runroot string               Path to the 'run directory' where all state information is stored
      --runtime string               Path to the OCI-compatible binary used to run containers, default is /usr/bin/runc
      --storage-driver string        Select which storage driver is used to manage storage of images and containers (default is overlay)
      --storage-opt strings          Used to pass an option to the storage driver
      --syslog                       Output logging information to syslog as well as the console
      --tmpdir string                Path to the tmp directory
      --trace                        Enable opentracing output
      --version                      Version for podman

Use "podman [command] --help" for more information about a command.
[root@podman-test ~]#

試しに DockerHub で公開されている hello-world コンテナを起動してみます。

[root@podman-test ~]# podman run docker.io/hello-world:latest
Trying to pull docker.io/hello-world:latest...Getting image source signatures
Copying blob 1b930d010525 done
Copying config fce289e99e done
Writing manifest to image destination
Storing signatures

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/

[root@podman-test ~]# 
[root@podman-test ~]# podman ps -a
CONTAINER ID  IMAGE                                 COMMAND  CREATED         STATUS                     PORTS  NAMES
4a830faa1d48  docker.io/library/hello-world:latest  /hello   11 seconds ago  Exited (0) 10 seconds ago         boring_bose
[root@podman-test ~]# 
[root@podman-test ~]# podman rm boring_bose 
4a830faa1d48f8a0436d9fdc8be840a99810a7d683340cfccfac66435fce4590
[root@podman-test ~]# 
[root@podman-test ~]# podman ps -a
CONTAINER ID  IMAGE  COMMAND  CREATED  STATUS  PORTS  NAMES
[root@podman-test ~]# 
[root@podman-test ~]# podman image ls
REPOSITORY                      TAG      IMAGE ID       CREATED        SIZE
docker.io/library/hello-world   latest   fce289e99eb9   5 months ago   6.14 kB
[root@podman-test ~]#

すると、上記の通り hello-world の Image を Pull して実行することができました。Image がローカルに Pull されていることも確認できます。

次に、NGINX のコンテナを起動してみます。サブコマンドだけでなく、”-d” や “-p” のオプションについても、docker コマンドと同じ感覚で使えるようです。

[root@podman-test ~]# podman run -d -p 8080:80 docker.io/nginx:latest
Trying to pull docker.io/nginx:latest...Getting image source signatures
Copying blob fc7181108d40 done
Copying blob 780053e98559 done
Copying blob c4277fc40ec2 done
Copying config 719cd2e3ed done
Writing manifest to image destination
Storing signatures
f7df535966a52ea10194521076c04ff20e3a814ed3390d34494bd4da797a2bbc
[root@podman-test ~]# 
[root@podman-test ~]# podman ps 
CONTAINER ID  IMAGE                           COMMAND               CREATED        STATUS            PORTS                 NAMES
f7df535966a5  docker.io/library/nginx:latest  nginx -g daemon o...  5 seconds ago  Up 4 seconds ago  0.0.0.0:8080->80/tcp  unruffled_jones
[root@podman-test ~]#

[root@podman-test ~]# podman run --help | grep "publish"
  -p, --publish strings                          Publish a container's port, or a range of ports, to the host (default [])
  -P, --publish-all                              Publish all exposed ports to random ports on the host interface
[root@podman-test ~]# 
[root@podman-test ~]# podman run --help | grep "detach"
  -d, --detach                                   Run container in background and print container ID
      --detach-keys [a-Z]                        Override the key sequence for detaching a container. Format is a single character [a-Z] or `ctrl-` where `` is one of: `a-z`, `@`, `^`, `[`, `\`, `]`, `^` or `_`
[root@podman-test ~]#

引数 “-p” で指定した 8080 port でリクエストを LISTEN していることも確認でき、リクエストを実行すると、NGINX からのレスポンス (デフォルトの index.html ファイルの内容) が返ってきます。

[root@podman-test ~]# netstat -tnlp | grep 8080        
tcp        0      0 0.0.0.0:8080            0.0.0.0:*               LISTEN      5967/conmon         
[root@podman-test ~]# 
[root@podman-test ~]# curl -XGET https://localhost:8080/
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
    body {
        width: 35em;
        margin: 0 auto;
        font-family: Tahoma, Verdana, Arial, sans-serif;
    }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="https://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="https://nginx.com/">nginx.com</a>.</p>

<p><em>Thank you for using nginx.</em></p>
</body>
</html>
[root@podman-test ~]#

また、podman exec を使ってコンテナ内でコマンドを実行 (今回はコンテナ内で bash コマンドを実行し、検証のために index.html の内容を書き替え) することもできました。

[root@podman-test ~]# podman exec -it unruffled_jones /bin/bash
root@f7df535966a5:/# 
root@f7df535966a5:/# echo "Podman Test" > /usr/share/nginx/html/index.html 
root@f7df535966a5:/# 
root@f7df535966a5:/# cat /usr/share/nginx/html/index.html 
Podman Test
root@f7df535966a5:/# 
root@f7df535966a5:/# exit
exit
[root@podman-test ~]# 
[root@podman-test ~]# curl -XGET https://localhost:8080/
Podman Test
[root@podman-test ~]#

コンテナの停止/削除等も docker と同じ様に stop/rm サブコマンドで実行できました。

[root@podman-test ~]# podman stop unruffled_jones
f7df535966a52ea10194521076c04ff20e3a814ed3390d34494bd4da797a2bbc
[root@podman-test ~]# 
[root@podman-test ~]# podman ps
CONTAINER ID  IMAGE  COMMAND  CREATED  STATUS  PORTS  NAMES
[root@podman-test ~]# 
[root@podman-test ~]# podman ps -a
CONTAINER ID  IMAGE                           COMMAND               CREATED         STATUS                    PORTS                 NAMES
f7df535966a5  docker.io/library/nginx:latest  nginx -g daemon o...  26 seconds ago  Exited (0) 7 seconds ago  0.0.0.0:8080->80/tcp  unruffled_jones
[root@podman-test ~]# 
[root@podman-test ~]# podman rm unruffled_jones 
f7df535966a52ea10194521076c04ff20e3a814ed3390d34494bd4da797a2bbc
[root@podman-test ~]#