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@s-yoshida

初心者のDocker事始め（Dockerfile編

Posted at

やること

  • 初心者のDocker事始めと同じことをDockerfileを使って行う。
  • その上で、Dockerfileを何となく雰囲気で理解する。

始める前の理解

「Dockerfile＝コンテナの構成を明記したファイル」的な感じでOKです。って言っても「で、結局何に使うの？」となりそうなので、「Dockerイメージを作るためのファイル」ってな感じでOKです。

Dockerfileの書式と命令

Dockerfileの書式は非常にシンプルです。

# コメント
命令 引数

例：

RUN echo 'Hello world!!'

命令はDockerfileリファレンスに書いてあるので参照ください。

Nginxのイメージを作成してみる

nginx:latestのイメージをベースに新しくイメージを作ってみます。vimが入ってない場合は適当に作成してください。

$ vim Dockerfile
FROM nginx
RUN apt-get update -y
RUN apt-get install -y vim
EXPOSE 80
$ docker build -t sample/nginx .
インストールログ Sending build context to Docker daemon 2.048kB Step 1/4 : FROM nginx latest: Pulling from library/nginx 27833a3ba0a5: Pull complete ea005e36e544: Pull complete d172c7f0578d: Pull complete Digest: sha256:e71b1bf4281f25533cf15e6e5f9be4dac74d2328152edf7ecde23abc54e16c1c Status: Downloaded newer image for nginx:latest ---> 27a188018e18 Step 2/4 : RUN apt-get update ---> Running in c2ec20e68c82 Get:1 http://security-cdn.debian.org/debian-security stretch/updates InRelease [94.3 kB] Ign:2 http://cdn-fastly.deb.debian.org/debian stretch InRelease Get:3 http://cdn-fastly.deb.debian.org/debian stretch-updates InRelease [91.0 kB] Get:4 http://security-cdn.debian.org/debian-security stretch/updates/main amd64 Packages [485 kB] Get:5 http://cdn-fastly.deb.debian.org/debian stretch Release [118 kB] Get:6 http://cdn-fastly.deb.debian.org/debian stretch Release.gpg [2434 B] Get:7 http://cdn-fastly.deb.debian.org/debian stretch-updates/main amd64 Packages [11.1 kB] Get:8 http://cdn-fastly.deb.debian.org/debian stretch/main amd64 Packages [7082 kB] Fetched 7884 kB in 3s (2056 kB/s) Reading package lists... Removing intermediate container c2ec20e68c82 ---> 391603069f19 Step 3/4 : RUN apt-get install -y vim ---> Running in daf96b852dec Reading package lists... Building dependency tree... Reading state information... The following additional packages will be installed: libgpm2 vim-common vim-runtime xxd Suggested packages: gpm ctags vim-doc vim-scripts The following NEW packages will be installed: libgpm2 vim vim-common vim-runtime xxd 0 upgraded, 5 newly installed, 0 to remove and 5 not upgraded. Need to get 6766 kB of archives. After this operation, 31.2 MB of additional disk space will be used. Get:1 http://cdn-fastly.deb.debian.org/debian stretch/main amd64 xxd amd64 2:8.0.0197-4+deb9u1 [132 kB] Get:2 http://cdn-fastly.deb.debian.org/debian stretch/main amd64 vim-common all 2:8.0.0197-4+deb9u1 [159 kB] Get:3 http://cdn-fastly.deb.debian.org/debian stretch/main amd64 libgpm2 amd64 1.20.4-6.2+b1 [34.2 kB] Get:4 http://cdn-fastly.deb.debian.org/debian stretch/main amd64 vim-runtime all 2:8.0.0197-4+deb9u1 [5407 kB] Get:5 http://cdn-fastly.deb.debian.org/debian stretch/main amd64 vim amd64 2:8.0.0197-4+deb9u1 [1034 kB] debconf: delaying package configuration, since apt-utils is not installed Fetched 6766 kB in 1s (4189 kB/s) Selecting previously unselected package xxd. (Reading database ... 7027 files and directories currently installed.) Preparing to unpack .../xxd_2%3a8.0.0197-4+deb9u1_amd64.deb ... Unpacking xxd (2:8.0.0197-4+deb9u1) ... Selecting previously unselected package vim-common. Preparing to unpack .../vim-common_2%3a8.0.0197-4+deb9u1_all.deb ... Unpacking vim-common (2:8.0.0197-4+deb9u1) ... Selecting previously unselected package libgpm2:amd64. Preparing to unpack .../libgpm2_1.20.4-6.2+b1_amd64.deb ... Unpacking libgpm2:amd64 (1.20.4-6.2+b1) ... Selecting previously unselected package vim-runtime. Preparing to unpack .../vim-runtime_2%3a8.0.0197-4+deb9u1_all.deb ... Adding 'diversion of /usr/share/vim/vim80/doc/help.txt to /usr/share/vim/vim80/doc/help.txt.vim-tiny by vim-runtime' Adding 'diversion of /usr/share/vim/vim80/doc/tags to /usr/share/vim/vim80/doc/tags.vim-tiny by vim-runtime' Unpacking vim-runtime (2:8.0.0197-4+deb9u1) ... Selecting previously unselected package vim. Preparing to unpack .../vim_2%3a8.0.0197-4+deb9u1_amd64.deb ... Unpacking vim (2:8.0.0197-4+deb9u1) ... Setting up xxd (2:8.0.0197-4+deb9u1) ... Setting up libgpm2:amd64 (1.20.4-6.2+b1) ... Processing triggers for libc-bin (2.24-11+deb9u4) ... Setting up vim-common (2:8.0.0197-4+deb9u1) ... Setting up vim-runtime (2:8.0.0197-4+deb9u1) ... Setting up vim (2:8.0.0197-4+deb9u1) ... update-alternatives: using /usr/bin/vim.basic to provide /usr/bin/vim (vim) in auto mode update-alternatives: using /usr/bin/vim.basic to provide /usr/bin/vimdiff (vimdiff) in auto mode update-alternatives: using /usr/bin/vim.basic to provide /usr/bin/rvim (rvim) in auto mode update-alternatives: using /usr/bin/vim.basic to provide /usr/bin/rview (rview) in auto mode update-alternatives: using /usr/bin/vim.basic to provide /usr/bin/vi (vi) in auto mode update-alternatives: warning: skip creation of /usr/share/man/fr/man1/vi.1.gz because associated file /usr/share/man/fr/man1/vim.1.gz (of link group vi) doesn't exist update-alternatives: warning: skip creation of /usr/share/man/it/man1/vi.1.gz because associated file /usr/share/man/it/man1/vim.1.gz (of link group vi) doesn't exist update-alternatives: warning: skip creation of /usr/share/man/pl/man1/vi.1.gz because associated file /usr/share/man/pl/man1/vim.1.gz (of link group vi) doesn't exist update-alternatives: warning: skip creation of /usr/share/man/ru/man1/vi.1.gz because associated file /usr/share/man/ru/man1/vim.1.gz (of link group vi) doesn't exist update-alternatives: warning: skip creation of /usr/share/man/ja/man1/vi.1.gz because associated file /usr/share/man/ja/man1/vim.1.gz (of link group vi) doesn't exist update-alternatives: warning: skip creation of /usr/share/man/man1/vi.1.gz because associated file /usr/share/man/man1/vim.1.gz (of link group vi) doesn't exist update-alternatives: using /usr/bin/vim.basic to provide /usr/bin/view (view) in auto mode update-alternatives: warning: skip creation of /usr/share/man/fr/man1/view.1.gz because associated file /usr/share/man/fr/man1/vim.1.gz (of link group view) doesn't exist update-alternatives: warning: skip creation of /usr/share/man/it/man1/view.1.gz because associated file /usr/share/man/it/man1/vim.1.gz (of link group view) doesn't exist update-alternatives: warning: skip creation of /usr/share/man/pl/man1/view.1.gz because associated file /usr/share/man/pl/man1/vim.1.gz (of link group view) doesn't exist update-alternatives: warning: skip creation of /usr/share/man/ru/man1/view.1.gz because associated file /usr/share/man/ru/man1/vim.1.gz (of link group view) doesn't exist update-alternatives: warning: skip creation of /usr/share/man/ja/man1/view.1.gz because associated file /usr/share/man/ja/man1/vim.1.gz (of link group view) doesn't exist update-alternatives: warning: skip creation of /usr/share/man/man1/view.1.gz because associated file /usr/share/man/man1/vim.1.gz (of link group view) doesn't exist update-alternatives: using /usr/bin/vim.basic to provide /usr/bin/ex (ex) in auto mode update-alternatives: warning: skip creation of /usr/share/man/fr/man1/ex.1.gz because associated file /usr/share/man/fr/man1/vim.1.gz (of link group ex) doesn't exist update-alternatives: warning: skip creation of /usr/share/man/it/man1/ex.1.gz because associated file /usr/share/man/it/man1/vim.1.gz (of link group ex) doesn't exist update-alternatives: warning: skip creation of /usr/share/man/pl/man1/ex.1.gz because associated file /usr/share/man/pl/man1/vim.1.gz (of link group ex) doesn't exist update-alternatives: warning: skip creation of /usr/share/man/ru/man1/ex.1.gz because associated file /usr/share/man/ru/man1/vim.1.gz (of link group ex) doesn't exist update-alternatives: warning: skip creation of /usr/share/man/ja/man1/ex.1.gz because associated file /usr/share/man/ja/man1/vim.1.gz (of link group ex) doesn't exist update-alternatives: warning: skip creation of /usr/share/man/man1/ex.1.gz because associated file /usr/share/man/man1/vim.1.gz (of link group ex) doesn't exist update-alternatives: using /usr/bin/vim.basic to provide /usr/bin/editor (editor) in auto mode update-alternatives: warning: skip creation of /usr/share/man/fr/man1/editor.1.gz because associated file /usr/share/man/fr/man1/vim.1.gz (of link group editor) doesn't exist update-alternatives: warning: skip creation of /usr/share/man/it/man1/editor.1.gz because associated file /usr/share/man/it/man1/vim.1.gz (of link group editor) doesn't exist update-alternatives: warning: skip creation of /usr/share/man/pl/man1/editor.1.gz because associated file /usr/share/man/pl/man1/vim.1.gz (of link group editor) doesn't exist update-alternatives: warning: skip creation of /usr/share/man/ru/man1/editor.1.gz because associated file /usr/share/man/ru/man1/vim.1.gz (of link group editor) doesn't exist update-alternatives: warning: skip creation of /usr/share/man/ja/man1/editor.1.gz because associated file /usr/share/man/ja/man1/vim.1.gz (of link group editor) doesn't exist update-alternatives: warning: skip creation of /usr/share/man/man1/editor.1.gz because associated file /usr/share/man/man1/vim.1.gz (of link group editor) doesn't exist Removing intermediate container daf96b852dec ---> fb4d084d4ad7 Step 4/4 : EXPOSE 80 ---> Running in b2a581711062 Removing intermediate container b2a581711062 ---> a37e2ae89839 Successfully built a37e2ae89839 Successfully tagged sample/nginx:latest 
$ docker images
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
sample/nginx        latest              a37e2ae89839        5 minutes ago       157MB
nginx               latest              27a188018e18        12 days ago         109MB

FROM nginx

imageを作成する時のベースになるイメージを記述します。WindowsとかLinuxを使う時に素のままではなくアプリをインストールしたり設定を変更すると思いますが、その「WindowsとかLinux」みたいな感じです。

RUN apt-get update -y
RUN apt-get install -y vim

Nginxのイメージにはvimが入っていないのでインストールします。この他にもRUNコマンドを使って様々なカスタマイズが可能です。

EXPOSE 80

接続用リッスンポート設定です。

作成したイメージからコンテナを作成する

$ docker run -d -p 8080:80 --name test-webserver sample/nginx
$ # docker exec -it test-webserver /bin/bash
$ # vim --help
VIM - Vi IMproved 8.0 (2016 Sep 12, compiled Sep 30 2017 18:21:38)
:
:
$ # exit
$ docker stop test-webserver

想定通りvimがインストールされてますね。
一旦コンテナとイメージを削除しておきます。

ディレクトリをマウントする

ディレクトリのマウントにはVOLUME命令を利用します。ただし、docker runの時のようにホストOS側のディレクトリは指定できません。Dockerfileを以下のように書き換えます。

FROM nginx
RUN echo "Hello, World" > /usr/share/nginx/html/hello.html
EXPOSE 80
VOLUME /usr/share/nginx/html

書き換えたらdocker build&docker runしてホストOSのどこが共有ディレクトリになっているのか調べます。

$ docker build -t sample/nginx .
$ docker run -d -p 8080:80 --name test-webserver sample/nginx
$ docker ps
CONTAINER ID        IMAGE               COMMAND                  CREATED              STATUS              PORTS                  NAMES
16e9545fffc3        sample/nginx        "nginx -g 'daemon of…"   About a minute ago   Up About a minute   0.0.0.0:8080->80/tcp   test-webserver
$ docker inspect 16e9545fffc3
:
:
"Mounts": [
    {
        "Type": "volume",
        "Name": "043f6045abb2ad6005675850f9d2b71e0e6ad5bd1f8fe33b526aa56daeab6479",
        "Source": "/var/lib/docker/volumes/043f6045abb2ad6005675850f9d2b71e0e6ad5bd1f8fe33b526aa56daeab6479/_data",
        "Destination": "/usr/share/nginx/html",
        "Driver": "local",
        "Mode": "",
        "RW": true,
        "Propagation": ""
    }
],
:
:

/var/lib/docker/volumes/043f6045abb2ad6005675850f9d2b71e0e6ad5bd1f8fe33b526aa56daeab6479/_dataがマウントされていることがわかります。が、そんなディレクトリは無い(´・ω・｀)
Docker for Macのvolumesの場所を参考にしながら進めて確認できた...けど、これじゃ使い勝手が悪い。とは言えdocker runする時に都度都度設定するのも面倒。さて、どうしたものか。

終わり

ってことで次回はdocker-compose。

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