第 8 章：使用 setup 取得節點資訊

使用 Playbooks 時，Ansible 會自動執行 setup module 以蒐集各個 Managed node 的 facts。對凍仁而言這個 facts 就如同系統變數般的存在，從 IP 位址、作業系統、CPU 等資訊。

Ad-Hoc Commands

一般會先使用 Ad-Hoc Commands 呼叫 setup 看看有哪些用的上的資訊，這對撰寫些較複雜的 Playbooks 時是很有用的。

使用 [chusiang/ansible-managed-node:ubuntu-14.04](https://hub.docker.com/r/chusiang/ansible-managed-node/) 這個 Docker image 作為 Managed node。

1. 藉由 less 快速搜尋所有的變數

ansible all -m setup | less

server1 | SUCCESS => {
   "ansible_facts": {
       "ansible_all_ipv4_addresses": [
           "172.19.0.2"
       ],
       "ansible_all_ipv6_addresses": [
           "fe80::42:acff:fe13:2"
       ],
       "ansible_architecture": "x86_64",
       "ansible_bios_date": "03/14/2014",
       "ansible_bios_version": "1.00",
       "ansible_cmdline": {
           "com.docker.database": "com.docker.driver.amd64-linux",
           "com.docker.driver": "com.docker.driver.amd64-linux,",
           "console": "ttyS0",
           "earlyprintk": "serial",
           "mobyplatform": "mac",
           "ntp": "gateway"
       },
       "ansible_date_time": {
           "date": "2016-12-13",
:

1. 搭配 filter 將發行版本 (distribution) 的資訊給過濾出來

ansible all -m setup -a "filter=ansible_distribution"

server1 | SUCCESS => {
   "ansible_facts": {
       "ansible_distribution": "Ubuntu",
       "ansible_distribution_major_version": "14",
       "ansible_distribution_release": "trusty",
       "ansible_distribution_version": "14.04"
   },
   "changed": false
}

1. 取得套件管理員的種類資訊，此例取得的值為 apt

ansible all -m setup -a "filter=ansible_pkg_mgr"

server1 | SUCCESS => {
   "ansible_facts": {
       "ansible_pkg_mgr": "apt"
   },
   "changed": false
}

撰寫跨 Linux distribution 的 Playbooks

取得 ansible_pkg_mgr 後，我們可以 Playbooks 裡加個判斷式使用

1. 建立支援 Debian, Ubuntu, CentOS 安裝 Vim 的 playbook

vim setup_vim.yml

- name: Setup the vim
 hosts: all
 become: true
 tasks:

   # Debian, Ubuntu.
   - name: install apt packages
     apt: name=vim state=present
     when: ansible_pkg_mgr == "apt"

   # CentOS.
   - name: install yum packages
     yum: name=vim-minimal state=present
     when: ansible_pkg_mgr == "yum"

# vim:ft=ansible :

1. 執行 playbook，且當條件不符時，即會跳過該 task

ansible-playbook setup_vim.yml

PLAY [Setup the vim] **************************************************

TASK [setup] **********************************************************
ok: [server1]

TASK [install apt packages] *******************************************
changed: [server1]

TASK [install yum packages] *******************************************
skipping: [server1]

PLAY RECAP ************************************************************
server1           : ok=2    changed=1    unreachable=0    failed=0