jenkins集成ansible注意事項Failed to connect to the host via ssh.

 　　在集成jenkins和ansible實現自動化部署時，root用戶下執行ansible命令時可以正常運行。由於是通過jenkins用戶去執行ansible命令，而jenkins用戶卻報如下異常：

XXXXXXX | UNREACHABLE! => {
    "changed": false, 
    "msg": "Failed to connect to the host via ssh.", 
    "unreachable": true
}

 　　找了好久也沒找到相應的解決辦法，后來在http://superuser.com/questions/1081609/ansible-how-to-set-a-default-ssh-user-for-all-hosts上找到了相應的解決辦法。

　　設置以root用戶執行ansible，將remote_user = root前的注釋符去掉，再次運行即可。

# default user to use for playbooks if user is not specified
# (/usr/bin/ansible will use current user as default)
remote_user = root

　　再次執行，成功返回執行信息。

-bash-4.2$ ansible webservers -m command -a "free -m"
xxxx | SUCCESS | rc=0 >>
             total       used       free     shared    buffers     cached
Mem:          1518        292       1225          0         42        125
-/+ buffers/cache:        125       1393
Swap:            0          0          0