Ansible 使用 setup 取得 Managed node 的 facts

2018-07-25 09:52 更新

使用 Playbooks 时，Ansible 会自动执行 setup module 以收集各个 Managed node 的 facts。对冻仁而言这个 facts 就如同系统变数般的存在，从 IP 位址、作业系统、CPU 等资讯应有尽有。

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.

Ad-Hoc Commands

冻仁一般会先使用 Ad-Hoc Commands 呼叫 setup 看看有哪些用的上的资讯，这对撰写些较复杂的 Playbooks 时是很有用的。

底下冻仁将使用 chusiang/ansible-managed-node:ubuntu-14.04 这个 Docker image 作为 Managed node。

借由 less 快速搜寻所有的变数。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 将发行版本 (distribution) 的资讯给过滤出来。

$ 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
}

取得套件管理员的种类资讯，此例取得的值为 apt。

$ ansible all -m setup -a "filter=ansible_pkg_mgr"
server1 | SUCCESS => {
   "ansible_facts": {
       "ansible_pkg_mgr": "apt"
   },
   "changed": false
}

撰写跨 Linux distribution 的 Playbooks

取得 ansible_pkg_mgr 后，我们可以 Playbooks 里加个判断式使用。

建立支持 Debian, Ubuntu, CentOS 安装 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 :

执行 playbook，且当条件不符时，即会跳过该 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

后话

setup module 是每位 Ansibler 一定会接触到的！我们可以善加利用它，并与各种需求搭配使用，这样会让 Playbooks 更具弹性且易于维护。

Ansible 使用 setup 取得 Managed node 的 facts

Ad-Hoc Commands

撰写跨 Linux distribution 的 Playbooks

后话

相关连结