如何在 Ansible Playbooks 中訪問系統信息（Facts）¶
默認情況下，在執行 playbook 中定義的任務集之前，Ansible 將花一些時間來收集有關正在配置的系統的信息。這些信息（稱為Facts）包含諸如網絡接口和地址、遠程節點上運行的操作系統和可用內存等詳細信息。
Ansible 以 JSON 格式存儲事實，項目按節點分組。要檢查您正在配置的系統有哪些類型的信息可用，您可以使用 ad hoc 命令運行 setup 模塊：
結果:
{
"ansible_facts": {
"ansible_all_ipv4_addresses": [
"10.0.2.15"
],
"ansible_all_ipv6_addresses": [
"fe80::45:8eff:fe95:1bba"
],
"ansible_apparmor": {
"status": "enabled"
},
"ansible_architecture": "x86_64",
"ansible_bios_date": "12/01/2006",
"ansible_bios_vendor": "innotek GmbH",
"ansible_bios_version": "VirtualBox",
"ansible_board_asset_tag": "NA",
"ansible_board_name": "VirtualBox",
"ansible_board_serial": "NA",
"ansible_board_vendor": "Oracle Corporation",
"ansible_board_version": "1.2",
"ansible_chassis_asset_tag": "NA",
"ansible_chassis_serial": "NA",
"ansible_chassis_vendor": "Oracle Corporation",
"ansible_chassis_version": "NA",
"ansible_cmdline": {
"BOOT_IMAGE": "/boot/vmlinuz-5.4.0-113-generic",
"console": "ttyS0",
"ro": true,
"root": "UUID=e42c9539-b31f-497a-98f5-47111033eed3"
},
"ansible_date_time": {
"date": "2022-06-08",
"day": "08",
"epoch": "1654679603",
"epoch_int": "1654679603",
"hour": "09",
"iso8601": "2022-06-08T09:13:23Z",
"iso8601_basic": "20220608T091323507293",
"iso8601_basic_short": "20220608T091323",
"iso8601_micro": "2022-06-08T09:13:23.507293Z",
"minute": "13",
"month": "06",
"second": "23",
"time": "09:13:23",
"tz": "UTC",
"tz_dst": "UTC",
"tz_offset": "+0000",
"weekday": "Wednesday",
"weekday_number": "3",
"weeknumber": "23",
"year": "2022"
},
"ansible_default_ipv4": {
"address": "10.0.2.15",
"alias": "enp0s3",
"broadcast": "10.0.2.255",
"gateway": "10.0.2.2",
"interface": "enp0s3",
"macaddress": "02:45:8e:95:1b:ba",
"mtu": 1500,
"netmask": "255.255.255.0",
"network": "10.0.2.0",
"type": "ether"
},
"ansible_default_ipv6": {}
},
...
...
}
此命令將輸出包含有關您的服務器信息的廣泛 JSON。要獲取該數據的子集，您可以使用 filter 參數並提供模式。例如，如果您想獲取有關遠程節點中所有 IPv4 地址的信息，可以使用以下命令：
結果:
demo-vm | SUCCESS => {
"ansible_facts": {
"ansible_all_ipv4_addresses": [
"10.0.2.15"
],
"ansible_default_ipv4": {
"address": "10.0.2.15",
"alias": "enp0s3",
"broadcast": "10.0.2.255",
"gateway": "10.0.2.2",
"interface": "enp0s3",
"macaddress": "02:45:8e:95:1b:ba",
"mtu": 1500,
"netmask": "255.255.255.0",
"network": "10.0.2.0",
"type": "ether"
},
"discovered_interpreter_python": "/usr/bin/python3"
},
"changed": false
}
一旦你找到了對你的自動化有用的 fact，你就可以相應地更新你的劇本。例如，以下 playbook 將打印出默認網絡接口的 IPv4 地址。從前面的命令輸出中，我們可以看到通過 Ansible 提供的 JSON 中的 ansible_default_ipv4.address 可以得到這個值。
在 ansible-practice 目錄中創建一個名為 playbook-03.yml 的新文件：
playbook-03.yml
---
- hosts: all
tasks:
- name: print facts
debug:
msg: "IPv4 address: {{ ansible_default_ipv4.address }}"
要在您的清單文件中的服務器上嘗試此 playbook，請使用您之前在運行我們的第一個示例時使用的相同連接參數運行 ansible-playbook。同樣，我們將使用一個名為 inventory 的清單文件連接到遠程服務器：
當您運行 playbook 時，您將在輸出中看到您的遠程服務器的 IPv4 地址，如預期的那樣：
PLAY [all] *******************************************************************************************************************
TASK [Gathering Facts] *******************************************************************************************************
ok: [demo-vm]
TASK [print facts] ***********************************************************************************************************
ok: [demo-vm] => {
"msg": "IPv4 address: 10.0.2.15"
}
PLAY RECAP *******************************************************************************************************************
demo-vm : ok=2 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
Facts 封裝了重要的元數據，您可以利用這些元數據更好地自定義您的劇本。要詳細了解您可以通過事實 facts 獲得的所有信息，請參閱 Ansible 官方文檔。