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 等資訊應有盡有。
官方文件介紹如下:
This module is automatically called by playbooks to gather useful variables about remote hosts that can be used in playbooks. It can also be executed directly by /usr/bin/ansible to check what variables are available to a host. Ansible provides many facts about the system, automatically.
凍仁一般會先使用 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。
底下凍仁將使用 chusiang/ansible-managed-node:ubuntu-14.04
這個 Docker image 作為 Managed node。
藉由 less 快速搜尋所有的變數。[^1]
$ 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",
:
搭配 filter
將發行版本 (distribution) 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
}
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
}
取得 ansible_pkg_mgr
後,我們可以 Playbooks 裡加入 when
的判斷式使用。
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 :
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
setup
module 是每位 Ansibler 一定會接觸到的!我們可以善加利用它,並與各種需求搭配使用,這樣會讓 Playbooks 更具彈性且易於維護。
[^1]: 在 less 裡我們可使用 /
+ 關鍵字 + Enter
進行搜尋。