使用Ansible轻松配置Linux基础设施

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"Ansible Configuration Management 是一本92页的书籍，由Daniel Hall撰写，它深入介绍了如何利用Ansible的强大功能轻松配置Linux基础设施。" Ansible是自动化运维领域中的一个热门工具，尤其在配置管理、应用程序部署和服务编排方面表现出色。这本书《Ansible Configuration Management》旨在帮助读者掌握如何有效地使用Ansible来管理和配置复杂的Linux环境。 1. **Ansible的基本概念** Ansible是一个基于Python的开源工具，以其易用性和无代理的特性而闻名。它使用SSH协议连接目标主机，无需在被管理节点上安装额外软件，这使得Ansible在跨平台管理中非常便捷。 2. **配置管理** 书中会详细讲解如何使用Ansible的YAML语法（称为Playbooks）来定义和执行配置任务。通过Playbooks，你可以声明性地定义服务器状态，确保系统配置的一致性。 3. **Ansible的模块** Ansible拥有丰富的模块库，涵盖了从文件管理、用户和组创建、包管理到服务控制等各种操作。书里将介绍如何利用这些模块实现自动化任务。 4. **角色（Roles）和变量** 角色是Ansible组织代码的一种方式，它允许你复用和共享配置代码。变量则是动态定制配置的关键，书中会解释如何定义和使用变量来适应不同环境的需求。 5. **库存（Inventory）管理** Ansible通过库存文件来定义管理的主机和组，书中会讲述如何编写和管理库存文件，以及如何使用动态库存源与AWS、OpenStack等云平台集成。 6. **Ansible Playbook的最佳实践** Daniel Hall可能会分享编写高效、可维护Playbooks的技巧，包括错误处理、条件语句、循环结构和任务控制等。 7. **部署和持续集成** 书中可能涵盖如何将Ansible集成到持续集成/持续部署(CI/CD)流程中，实现自动化的应用部署。 8. **安全与最佳实践** 安全是任何自动化过程的重要考量，书中会讨论如何在使用Ansible时保护敏感信息，如加密密码和使用安全的凭证存储。 9. **案例研究和示例** 作者可能会提供实际的场景分析和代码示例，帮助读者更好地理解和应用Ansible。 10. **故障排查** 了解如何诊断和解决Ansible运行时的问题也是至关重要的，书中可能会包含一些常见的问题和解决方案。请注意，尽管此书可能提供了商标信息，但准确性无法得到保证，读者在实际使用中应自行核实涉及的公司和产品信息。此外，虽然书中的信息尽力保证准确，但作者和出版商对因使用本书内容可能造成的任何直接或间接损害不承担责任。

Getting Started with Ansible

[ 6 ]

The following are the topics covered in this chapter:

• Installing Ansible

• Conguring Ansible

• Using Ansible from the command line

• How to get help

Installation methods

If you want to use Ansible to manage a set of existing machines or infrastructure,

you will likely want to use whatever package manager is included on those systems.

This means that you will get updates for Ansible as your distribution updates it,

which may lag several versions behind other methods. However, it doesn't mean

that you will be running a version that has been tested to work on the system you are

using.

If you run an existing infrastructure but need a newer version of Ansible, you can

install Ansible via pip. Pip is a tool used to manage packages of Python software and

libraries. Ansible releases are pushed to pip as soon as they are released, so if you are

up to date with pip, you should always be running the latest version.

If you imagine yourself developing lots of modules and possibly contributing back

to Ansible, you should be running a checked-out version. As you will be running the

latest and least tested version of Ansible, you may experience a hiccup or two.

Installing from your distribution

Most modern distributions include a package manager that automatically manages

package dependencies and updates for you. This makes installing Ansible via your

package manager by far the easiest way to get started with Ansible; usually it takes

only a single command. It will also be updated as you update your machine, though

it may be a version or two behind. The following are the commands to install Ansible

on the most common distributions. If you are using something different, refer to the

user guide for your package or your distribution's package lists.

• Fedora, RHEL, CentOS, and compatible:

$ yum install ansible

• Ubuntu, Debian, and compatible: $ apt-get install ansible

Chapter 1

[ 7 ]

Installing from pip

Pip, like a distribution's package manager, will handle nding, installing, and

updating the packages you ask for and its dependencies. This makes installing

Ansible via pip as easy as installing from your package manager. It should be noted,

however, that it will not be updated with your operating system. Additionally,

updating your operating system may break your Ansible installation; however,

this is unlikely. The following is the command to install Ansible via pip:

$ pip install ansible

Installing from the source code

Installing from the source code is a great way to get the latest version, but it may not

be tested as correctly as released versions. You also will need to take care of updating

to newer versions yourself and making sure that Ansible will continue to work with

your operating system updates. To clone the git repository and install it, run the

following commands. You may need root access to your system to do this:

$ git clone git://github.com/ansible/ansible.git

$ cd ansible

$ sudo make install

Setting up Ansible

Ansible needs to be able to get an inventory of the machines that you want to congure

in order to manage them. This can be done in many ways due to inventory plugins.

Several different inventory plugins are included with the base install. We will go over

these later in the book, but for now we will cover the simple hosts le inventory.

The default Ansible inventory le is named hosts and placed in

/etc/ansible. It is

formatted like an INI le. Group names are enclosed in square braces, and everything

underneath it, down to the next group heading, gets assigned to that group. Machines

can be in many groups at one time. Groups are used to allow you to congure many

machines at once. You can use a group instead of a hostname as a host pattern in later

examples, and Ansible will run the module on the entire group at once.

In the following example, we have three machines in a group named

webservers,

namely site01, site02, and site01-dr. We also have a production group that

consists of site01, site02, db01, and bastion.

[webservers]

site01

site02

Chapter 1

[ 9 ]

To set the username in the inventory le, simply append ansible_ssh_user to the

line in the inventory. For example, the next code section shows an inventory where

the site01 host uses the username root and the site02 host uses the username

daniel. There are also other variables you can use. The ansible_ssh_host le

allows you to set a different hostname and the ansible_ssh_port le allows you

to set a different port; this is demonstrated on the site01-dr host. Finally, the

db01 host uses the username fred and also sets a private key using ansible_ssh_

private_key_file

[webservers] #1

site01 ansible_ssh_user=root #2

site02 ansible_ssh_user=daniel #3

site01-dr ansible_ssh_host=site01.dr ansible_ssh_port=65422 #4

[production] #5

site01 #6

site02 #7

db01 ansible_ssh_user=fred

ansible_ssh_private_key_file=/home/fred/.ssh.id_rsa bastion #8

If you aren't comfortable with giving Ansible direct access to the root account on

the managed machines, or your machine does not allow SSH access to the root

account (such as Ubuntu's default conguration), you can congure Ansible to

obtain root access using sudo. Using Ansible with sudo means that you can enforce

auditing the same way you would otherwise. Conguring Ansible to use sudo is as

simple as it is to congure the port, except that it requires sudo to be congured on

the managed machine.

The rst step is to add a line to the

/etc/sudoers le; this may already be set up if

you choose to use your own account. You can use a password with sudo, or you can

use a passwordless sudo. If you decide to use a password, you will need to use the

-k argument to Ansible, or set the ask_sudo_pass value to true in /etc/ansible/

ansible.cfg

. To make Ansible use sudo, add --sudo to the command line.

First steps with Ansible

Ansible modules take arguments in key value pairs that look similar to key=value,

perform a job on the remote server, and return information about the job as JSON.

The key value pairs allow the module to know what to do when requested. They can

be hard coded values, or in playbooks they can use variables, which will be covered

in Chapter 2, Simple Playbooks. The data returned from the module lets Ansible know

if anything changed or if any variables should be changed or set afterwards.

Getting Started with Ansible

[ 10 ]

Modules are usually run within playbooks as this lets you chain many together, but

they can also be used on the command line. Previously, we used the ping command

to check that Ansible had been correctly setup and was able to access the congured

node. The ping module only checks that the core of Ansible is able to run on the

remote machine but effectively does nothing.

A slightly more useful module is called setup. This module connects to the

congured node, gathers data about the system, and then returns those values. This

isn't particularly handy for us while running from the command line, however, in a

playbook you can use the gathered values later in other modules.

To run Ansible from the command line, you need to pass two things, though usually

three. First is a host pattern to match the machine that you want to apply the module

to. Second you need to provide the name of the module that you wish to run and

optionally any arguments that you wish to give to the module. For the host pattern,

you can use a group name, a machine name, a glob, and a tilde (~), followed by a

regular expression matching hostnames, or to symbolize all of these, you can either

use the word

all or simply *.

To run the

setup module on one of your nodes, you need the following

command line:

$ ansible machinename -u root -k -m setup

The setup module will then connect to the machine and give you a number of useful

facts back. All the facts provided by the setup module itself are prepended with

ansible_ to differentiate them from variables. The following is a table of the most

common values you will use, example values, and a short description of the elds:

Field Example Description

ansible_architecture x86_64

The architecture of the managed

machine

ansible_distribution CentOS

The Linux or Unix distribution on

the managed machine

ansible_distribution_

version

6.3

The version of the preceding

distribution

ansible_domain example.com

The domain name part of the

server's hostname

ansible_fqdn machinename.

example.com

This is the fully qualified domain

name of the managed machine

ansible_interfaces ["lo", "eth0"]

A list of all the interfaces the

machine has, including the

loopback interface

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