Dockerで手元のイメージから派生したイメージを作る

BaseとなるDockerfile

Dockerfile

https://github.com/piuccio/cowsay を グローバルインストールしておく

FROM node:14
RUN npm install -g cowsay

ビルドしてcowsay-imageでタグ付けする

$ docker build -t cowsay-image .

$ docker image ls                 
REPOSITORY                                                         TAG       IMAGE ID       CREATED         SIZE
cowsay-image                                                       latest    2d25113e504d   3 minutes ago   946MB

コンテナを立ち上げてbashに入って実際にcowsayがグローバルインストールしてあるか確認

$ docker run -it cowsay-image bash
root@8888888:/# cowsay hoge
 ______
< hoge >
 ------
        \   ^__^
         \  (oo)\_______
            (__)\       )\/\
                ||----w |
                ||     ||
root@8888888:/# 

Baseを元に派生したイメージを作成する

Dockerfile

ローカルで派生したイメージを作るにはFROMに先程作成したイメージ名を指定するだけ！！

FROM cowsay-image
CMD [ "cowsay", "hoge" ]

$ docker run -it evolution-cowsay   
 ______
< hoge >
 ------
        \   ^__^
         \  (oo)\_______
            (__)\       )\/\
                ||----w |
                ||     ||

CMDなどに設定するコマンドを色々試したい時

bashで色々試せるので、Baseイメージ内でコマンド打って検証する

$ docker run -it cowsay-image bash
root@ce25bb3685b6:/# cowsay

Usage: cowsay [-e eye_string] [-f cowfile] [-h] [-l] [-n] [-T tongue_string] [-W
column] [-bdgpstwy] text

If any command-line arguments are left over after all switches have been
processed, they become the cow's message.

If the program is invoked as cowthink then the cow will think its message
instead of saying it.


Options:
  --version   Show version number                                      [boolean]
  -e          Select the appearance of the cow's eyes.           [default: "oo"]
  -T          The tongue is configurable similarly to the eyes through -T and
              tongue_string.                                     [default: "  "]
  -W          Specifies roughly where the message should be wrapped. The default
              is equivalent to -W 40 i.e. wrap words at or before the 40th
              column.                                     [number] [default: 40]
  -f          Specifies a cow picture file (''cowfile'') to use. It can be
              either a path to a cow file or the name of one of cows included in
              the package.                                  [default: "default"]
  --think     Think the message instead of saying it aloud.            [boolean]
  -b          Mode: Borg                                               [boolean]
  -d          Mode: Dead                                               [boolean]
  -g          Mode: Greedy                                             [boolean]
  -p          Mode: Paranoia                                           [boolean]
  -s          Mode: Stoned                                             [boolean]
  -t          Mode: Tired                                              [boolean]
  -w          Mode: Wired                                              [boolean]
  -y          Mode: Youthful                                           [boolean]
  -h, --help  Show help                                                [boolean]
  -n          If it is specified, the given message will not be word-wrapped.
                                                                       [boolean]
  -r          Select a random cow                                      [boolean]
  -l          List all cowfiles included in this package.              [boolean]
root@ce25bb3685b6:/# cowsay -b fugo
 ______
< fugo >
 ------
        \   ^__^
         \  (==)\_______
            (__)\       )\/\
                ||----w |
                ||     ||
root@ce25bb3685b6:/# cowsay -w fugo
 ______
< fugo >
 ------
        \   ^__^
         \  (OO)\_______
            (__)\       )\/\
                ||----w |
                ||     ||
root@ce25bb3685b6:/# cowsay -y fugo   
 ______
< fugo >
 ------
        \   ^__^
         \  (..)\_______
            (__)\       )\/\
                ||----w |
                ||     ||
root@ce25bb3685b6:/# cowsay -t fugo
 ______
< fugo >
 ------
        \   ^__^
         \  (--)\_______
            (__)\       )\/\
                ||----w |
                ||     ||