現代 IT 人一定要知道的 Ansible 自動化組態技巧
13. 怎麼使用 setup 取得 Managed node 的 facts?
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.
Ad-Hoc Commands
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) 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 }
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。
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
後語
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。
相關連結
1. 在 less 裡我們可使用/
+ 關鍵字 +Enter
進行搜尋。 ↩