amazon-linux-extras

CentOS7 ベースの AmazonLinux2 なるものに ansible を入れようとしたら、以下のようなアドバイスをいただきました。

```console
ec2-user@AmazonLinux2:~$ sudo yum install ansible
読み込んだプラグイン:extras_suggestions, langpacks, priorities, update-motd
パッケージ ansible は利用できません。
エラー: 何もしません

ansible is available in Amazon Linux Extra topic "ansible2"

To use, run
# sudo amazon-linux-extras install ansible2

Learn more at
https://aws.amazon.com/amazon-linux-2/faqs/#Amazon_Linux_Extras
```
AmazonLinux2 には amazon-linux-extras なるコマンドがあるみたいです。
ansible は ansible2 というパッケージ名ですんなり入ったんですが、このコマンドは、他にも「こんなのありますよ～」というご紹介をしてくれるみたいです。概観するには便利かも。

```console
ec2-user@AmazonLinux2:~$ amazon-linux-extras
  0  ansible2=latest          enabled      [ =2.4.2  =2.4.6  =2.8 ]
  2  httpd_modules            available    [ =1.0 ]
  3  memcached1.5             available    \
        [ =1.5.1  =1.5.16  =1.5.17 ]
  5  postgresql9.6            available    [ =9.6.6  =9.6.8 ]
  6  postgresql10             available    [ =10 ]
  8  redis4.0                 available    [ =4.0.5  =4.0.10 ]
  9  R3.4                     available    [ =3.4.3 ]
 10  rust1                    available    \
        [ =1.22.1  =1.26.0  =1.26.1  =1.27.2  =1.31.0  =1.38.0 ]
 11  vim                      available    [ =8.0 ]
 13  ruby2.4                  available    [ =2.4.2  =2.4.4  =2.4.7 ]
 15  php7.2                   available    \
        [ =7.2.0  =7.2.4  =7.2.5  =7.2.8  =7.2.11  =7.2.13  =7.2.14
          =7.2.16  =7.2.17  =7.2.19  =7.2.21  =7.2.22  =7.2.23
          =7.2.24 ]
 16  php7.1                   available    \
        [ =7.1.22  =7.1.25  =7.1.27  =7.1.28  =7.1.30  =7.1.31
          =7.1.32  =7.1.33 ]
 17  lamp-mariadb10.2-php7.2  available    \
        [ =10.2.10_7.2.0  =10.2.10_7.2.4  =10.2.10_7.2.5
          =10.2.10_7.2.8  =10.2.10_7.2.11  =10.2.10_7.2.13
          =10.2.10_7.2.14  =10.2.10_7.2.16  =10.2.10_7.2.17
          =10.2.10_7.2.19  =10.2.10_7.2.21  =10.2.10_7.2.22
          =10.2.10_7.2.23  =10.2.10_7.2.24 ]
 18  libreoffice              available    [ =5.0.6.2_15  =5.3.6.1 ]
 19  gimp                     available    [ =2.8.22 ]
 20  docker=latest            enabled      \
        [ =17.12.1  =18.03.1  =18.06.1  =18.09.9 ]
 21  mate-desktop1.x          available    [ =1.19.0  =1.20.0 ]
 22  GraphicsMagick1.3        available    [ =1.3.29  =1.3.32 ]
 23  tomcat8.5                available    \
        [ =8.5.31  =8.5.32  =8.5.38  =8.5.40  =8.5.42 ]
 24  epel                     available    [ =7.11 ]
 25  testing                  available    [ =1.0 ]
 26  ecs                      available    [ =stable ]
 27  corretto8                available    \
        [ =1.8.0_192  =1.8.0_202  =1.8.0_212  =1.8.0_222  =1.8.0_232 ]
 28  firecracker              available    [ =0.11 ]
 29  golang1.11               available    \
        [ =1.11.3  =1.11.11  =1.11.13 ]
 30  squid4                   available    [ =4 ]
 31  php7.3                   available    \
        [ =7.3.2  =7.3.3  =7.3.4  =7.3.6  =7.3.8  =7.3.9  =7.3.10
          =7.3.11 ]
 32  lustre2.10               available    [ =2.10.5 ]
 33  java-openjdk11           available    [ =11 ]
 34  lynis                    available    [ =stable ]
 35  kernel-ng                available    [ =stable ]
 36  BCC                      available    [ =0.x ]
 37  mono                     available    [ =5.x ]
 38  nginx1                   available    [ =stable ]
 39  ruby2.6                  available    [ =2.6 ]
 40  mock                     available    [ =stable ]
 41  postgresql11             available    [ =11 ]
```
アプリの実行環境を作るためと割り切れる場合はこっちの方が便利そうですね。ただ、CentOS7 を使った構築を作るためのテスト環境としては、「混ぜるな危険」状態になりそうで、ちょっと微妙な感じです。