變數查詢

1. rescue 是在 block 執行出錯時才執行，判斷是否執行出錯，要先得知執行內容有哪些參數，使用 setup 模組過濾變數字串來查詢。例如：查詢主機 dev 的 ansible_lvm 相關參數如如下：

   ceuser@deyu:~/ansible_pb$ ansible dev -m setup -a "filter=ansible_lvm"
   kvm11 | SUCCESS => {
       "ansible_facts": {
           "ansible_lvm": {
               "lvs": {
                   "root": {
                       "size_g": "3.32",
                       "vg": "vg_kvm11"
                   },
                   "swap": {
                       "size_g": "0.09",
                       "vg": "vg_kvm11"
                   }
               },
               "pvs": {
                   "/dev/vda3": {
                       "free_g": "0",
                       "size_g": "3.41",
                       "vg": "vg_kvm11"
                   },
                   "/dev/vda4": {
                       "free_g": "0.29",
                       "size_g": "0.29",
                       "vg": "fieldwork"
                   },
                   "/dev/vdb1": {
                       "free_g": "1.49",
                       "size_g": "1.49",
                       "vg": "vg1"
                   }
               },
               "vgs": {
                   "fieldwork": {
                       "free_g": "0.29",
                       "num_lvs": "0",
                       "num_pvs": "1",
                       "size_g": "0.29"
                   },
                   "vg_kvm11": {
                       "free_g": "0",
                       "num_lvs": "2",
                       "num_pvs": "1",
                       "size_g": "3.41"
                   }
               }
           },
           "discovered_interpreter_python": "/usr/bin/python3"
       },
       "changed": false
   }