# 远程节点的系统变量(facts)

ansible会通过module setup来收集主机的系统信息，这些收集到的系统信息叫做facts，这些facts信息可以直接以变量的形式使用。

哪些facts变量可以引用呢？在命令行上通过调用setup module命令可以查看

```
$ ansible all -m setup -u root
```

怎样在playbook中使用facts变量呢，答案是直接使用：

```
---
- hosts: all
  user: root
  tasks:
  - name: echo system
    shell: echo {{ ansible_os_family }}
  - name install ntp on Debian linux
    apt: name=git state=installed
    when: ansible_os_family == "Debian"
  - name install ntp on redhat linux
    yum: name=git state=present
    when: ansible_os_family == "RedHat"
```

## 使用复杂facts变量

一般在系统中收集到如下的信息，复杂的、多层级的facts变量如何使用呢？

```
...
        "ansible_ens3": {
            "active": true, 
            "device": "ens3", 
            "ipv4": {
                "address": "10.66.192.234", 
                "netmask": "255.255.254.0", 
                "network": "10.66.192.0"
            }, 
            "ipv6": [
                {
                    "address": "2620:52:0:42c0:5054:ff:fef2:e2a3", 
                    "prefix": "64", 
                    "scope": "global"
                }, 
                {
                    "address": "fe80::5054:ff:fef2:e2a3", 
                    "prefix": "64", 
                    "scope": "link"
                }
            ], 
            "macaddress": "52:54:00:f2:e2:a3", 
            "module": "8139cp", 
            "mtu": 1500, 
            "promisc": false, 
            "type": "ether"
        }, 
...
```

那么可以通过下面的两种方式访问复杂的变量中的子属性:

中括号：

```
{{ ansible_ens3["ipv4"]["address"] }}
```

点号：

```
{{ ansible_ens3.ipv4.address }}
```

## 关闭facts

在Playbook中,如果写gather\_facts来控制是否收集远程系统的信息.如果不收集系统信息,那么上面的变量就不能在该playybook中使用了.

```
- hosts: whatever
  gather_facts: no
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://ansible-book.gitbook.io/ansible-first-book/ansible-jin-jie/ansible-de-jiao-ben-playbook/bian-liang/yuan-cheng-jie-dian-de-xi-tong-bian-liang-facts.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.