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知识点：-v -vv -vvv选项

知识点：ansible执行原理

ansible与puppet等相比，其号称是agentless的，而且这个也确实在很多台机器上进行运维时不用一台一台安装或者升级客户端确实带来了一定的便利。Ansible为什么能够实现不需要agent呢，原理在于其将要执行的命令或者脚本通过sftp的方式传到要执行的对象机器，然后通过ssh远程执行，执行之后清理现场将sftp传过去的文件删除，好像一切都没有发生过的一样，这个就是ansible不需要agent的原理。

口说无凭，上实例。

[root@host31 ~]# ansible host32 -m command -a "echo hello world" -vUsing /etc/ansible/ansible.cfg as config filehost32 | SUCCESS | rc=0 >>hello world[root@host31 ~]#

这是一个更为简单的helloworld，-v的选项是显示出详细信息。ansible支持三种显示信息的方式

-v

-vv

-vvv

我们接下来使用-vvv来再看ansible是如何动作的

[root@host31 ~]# ansible host32 -m command -a "echo hello world" -vvvUsing /etc/ansible/ansible.cfg as config file
   
     ESTABLISH SSH CONNECTION FOR USER: None
    
      SSH: EXEC ssh -C -q -o ControlMaster=auto -o ControlPersist=60s -o KbdInteractiveAuthentication=no -o PreferredAuthentications=gssapi-with-mic,gssapi-keyex,hostbased,publickey -o PasswordAuthentication=no -o ConnectTimeout=10 -o ControlPath=/root/.ansible/cp/ansible-ssh-%h-%p-%r host32 '/bin/sh -c '"'"'( umask 77 && mkdir -p "` echo $HOME/.ansible/tmp/ansible-tmp-1469831679.43-224816968104064 `" && echo ansible-tmp-1469831679.43-224816968104064="` echo $HOME/.ansible/tmp/ansible-tmp-1469831679.43-224816968104064 `" ) && sleep 0'"'"''
     
       PUT /tmp/tmpUjtNjh TO /root/.ansible/tmp/ansible-tmp-1469831679.43-224816968104064/command
      
        SSH: EXEC sftp -b - -C -o ControlMaster=auto -o ControlPersist=60s -o KbdInteractiveAuthentication=no -o PreferredAuthentications=gssapi-with-mic,gssapi-keyex,hostbased,publickey -o PasswordAuthentication=no -o ConnectTimeout=10 -o ControlPath=/root/.ansible/cp/ansible-ssh-%h-%p-%r '[host32]'
       
         ESTABLISH SSH CONNECTION FOR USER: None
        
          SSH: EXEC ssh -C -q -o ControlMaster=auto -o ControlPersist=60s -o KbdInteractiveAuthentication=no -o PreferredAuthentications=gssapi-with-mic,gssapi-keyex,hostbased,publickey -o PasswordAuthentication=no -o ConnectTimeout=10 -o ControlPath=/root/.ansible/cp/ansible-ssh-%h-%p-%r -tt host32 '/bin/sh -c '"'"'LANG=en_US.UTF-8 LC_ALL=en_US.UTF-8 LC_MESSAGES=en_US.UTF-8 /usr/bin/python /root/.ansible/tmp/ansible-tmp-1469831679.43-224816968104064/command; rm -rf "/root/.ansible/tmp/ansible-tmp-1469831679.43-224816968104064/" > /dev/null 2>&1 && sleep 0'"'"''host32 | SUCCESS | rc=0 >>hello world[root@host31 ~]#
        
       
      
     
    
   

分析

[root@host31 ~]# ansible host32 -m command -a “echo hello world” -vvv

Using /etc/ansible/ansible.cfg as config file

ESTABLISH SSH CONNECTION FOR USER: None

SSH: EXEC ssh -C -q -o ControlMaster=auto -o ControlPersist=60s -o KbdInteractiveAuthentication=no -o PreferredAuthentications=gssapi-with-mic,gssapi-keyex,hostbased,publickey -o PasswordAuthentication=no -o ConnectTimeout=10 -o ControlPath=/root/.ansible/cp/ansible-ssh-%h-%p-%r host32 ‘/bin/sh -c ‘”’”’( umask 77 && mkdir -p “echo $HOME/.ansible/tmp/ansible-tmp-1469831679.43-224816968104064” && echo ansible-tmp-1469831679.43-224816968104064=”echo $HOME/.ansible/tmp/ansible-tmp-1469831679.43-224816968104064” ) && sleep 0’”’””

PUT /tmp/tmpUjtNjh TO /root/.ansible/tmp/ansible-tmp-1469831679.43-224816968104064/command

到此处我们可以清晰地看到ansible做了两件事情

SSH: EXEC sftp -b - -C -o ControlMaster=auto -o ControlPersist=60s -o KbdInteractiveAuthentication=no -o PreferredAuthentications=gssapi-with-mic,gssapi-keyex,hostbased,publickey -o PasswordAuthentication=no -o ConnectTimeout=10 -o ControlPath=/root/.ansible/cp/ansible-ssh-%h-%p-%r ‘[host32]’

到此处可以看到通过sftp传送到host32

ESTABLISH SSH CONNECTION FOR USER: None

SSH: EXEC ssh -C -q -o ControlMaster=auto -o ControlPersist=60s -o KbdInteractiveAuthentication=no -o PreferredAuthentications=gssapi-with-mic,gssapi-keyex,hostbased,publickey -o PasswordAuthentication=no -o ConnectTimeout=10 -o ControlPath=/root/.ansible/cp/ansible-ssh-%h-%p-%r -tt host32 ‘/bin/sh -c ‘”’“‘LANG=en_US.UTF-8 LC_ALL=en_US.UTF-8 LC_MESSAGES=en_US.UTF-8 /usr/bin/python /root/.ansible/tmp/ansible-tmp-1469831679.43-224816968104064/command; rm -rf “/root/.ansible/tmp/ansible-tmp-1469831679.43-224816968104064/” > /dev/null 2>&1 && sleep 0’”’””

通过ssh远程执行，执行之后清理现场将sftp传过去的文件删除

host32 | SUCCESS | rc=0 >>

总结：

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