ansible 2.7.9使用host_vars（未定义变量）的问题

Question

Ansible 2.7.9没有使用host_vars

Ive设置一个非常简单的设置，有3个主机，主要是为了测试目的。我有主人：

- ansible1 (this is where I store the code)
- ansible2
- ansible3

我的库存：

[ansible@ansible1 ~]$ cat /etc/ansible/hosts
[common]
ansible1
ansible2
ansible3

[ansible@ansible1 ~]$ cat /etc/ansible/ansible.cfg
[defaults]
roles_path = /etc/ansible/roles
inventory  = /etc/ansible/hosts
[privilege_escalation]
[paramiko_connection]
[ssh_connection]
pipelining = True
control_path = /tmp/ansible-ssh-%%h-%%p-%%r
pipelining = False
[accelerate]
[selinux]
[colors]

[ansible@ansible1 ~]$ ls /etc/ansible/roles/
common  common.retry  common.yml
[ansible@ansible1 ~]$ cat /etc/ansible/roles/common.yml
--- # Playbook for webservers
- hosts: common
  roles:
    - common
[ansible@ansible1 ~]$

[ansible@ansible1 ~]$ cat /etc/ansible/roles/common/tasks/main.yml
- name: test ansible1
  lineinfile:
    dest: /tmp/ansible.txt
    create: yes
    line: "{{ myvar }}"
- name: set ansible2
  lineinfile:
    dest: /tmp/ansible2.txt
    create: yes
    line: "hi"
[ansible@ansible1 ~]$

[ansible@ansible1 ~]$ cat /etc/ansible/roles/common/vars/main.yml
copyright_msg: "Copyrighta 2019"
myvar: "value of myvar from common/vars"

[ansible@ansible1 ~]$ ls /etc/ansible/hosts_vars/
ansible2.yml
[ansible@ansible1 ~]$ cat /etc/ansible/hosts_vars/ansible2.yml
myvar: "myvar from host_vars"
[ansible@ansible1 ~]$

[ansible@ansible1 ~]$ ansible-playbook /etc/ansible/roles/common.yml --limit ansible2

PLAY [common] ******************************************************************

TASK [Gathering Facts] *********************************************************
ok: [ansible2]

TASK [common : test ansible1] **************************************************
changed: [ansible2]

TASK [common : set ansible2] ***************************************************
changed: [ansible2]

PLAY RECAP *********************************************************************
ansible2                   : ok=3    changed=2    unreachable=0    failed=0

我看到包含myvar内容的文件：

[root@ansible2 ~]# cat /tmp/ansible.txt
value of myvar from common/vars
[root@ansible2 ~]#

但我不明白为什么它不从/etc/ansible/hosts_vars/ansible2.yml中取值，事实上，如果我注释/etc/ansible/roles/common/vars/main.yml中的行，它表示未定义变量：

[ansible@ansible1 ansible]$ cat /etc/ansible/roles/common/vars/main.yml
copyright_msg: "Copyrighta 2019"
myvar: "value of myvar from common/vars"

Answer 1

Ansible对来自VAR的值使用该优先级：

From least to most important
role defaults
inventory file or script group vars
inventory group_vars/all
playbook group_vars/all
inventory group_vars/*
playbook group_vars/*
inventory file or script host vars
inventory host_vars/*
playbook host_vars/*
host facts
play vars
play vars_prompt
play vars_files
role vars (defined in role/vars/main.yml)
block vars (only for tasks in block)
task vars (only for the task)
role (and include_role) params
include params
include_vars
set_facts / registered vars
extra vars (always win precedence)

所以最好不要使用roles/var，因为它优先于host_vars，所以我应该使用roles/defaults，它的优先级较低。