April 2016
Intermediate to advanced
364 pages
7h 54m
Japanese
Content preview from 初めてのAnsible
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7
1.4 Ansible がすばらしい理由
が、
Ansible
の本当のパワーは、同梱されているモジュール群にあります。モジュールを使えば、
パッケージのインストール、サービスの再起動、設定ファイルのコピーといったタスクを実行でき
ます。
後ほど見ていくように、
Ansible
のモジュールは宣言的です。モジュールは、サーバーのあるべ
き状態を記述するために使います。例えば、以下のように
user
モジュールを起動すれば、「
web
」
グループに「
deploy
」というアカウントが存在することが保証されます。
user: name=deploy group=web
モジュールは冪等でもあります。もしも「
deploy
」ユーザーが存在しなければ、
Ansible
はその
ユーザーを作成します。もしすでに存在していたなら、
Ansible
は何もしません。冪等性が優れた
性質なのは、サーバーに対して
Ansible
の
playbook
を何回も実行しても安全ということを意味す
るからです。これは、シェルスクリプトを自作するアプローチと比べると、大きな改善です。そう
いったスクリプトは、
2
回実行してしまうと、（おそらくは意図していなかった）別の効果を生ん
でしまうかもしれません。
収斂について
設定管理に関する書籍では、しばしば収斂という概念が取り上げられています。設定管理における収斂
は、Mark Burgess と、彼が作り出した設定管理システムの CFEngine に最も密接に関連づけられていま
す。
収斂性を持つ設定管理システムは、サーバーを希望する状態に持っていくために、何度も動作することに ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.