我的jenkins从节点离线，日志如下：

[06/11/15 09:02:52] [SSH] Opening SSH connection to <ip>.
ERROR: Server rejected the 1 private key(s) for jenkins (credentialId:d7a17c00-1300-4cf3-8cf5-810b3297ebc6/method:publickey)
[06/11/15 09:02:52] [SSH] Authentication failed.
hudson.AbortException: Authentication failed.
    at hudson.plugins.sshslaves.SSHLauncher.openConnection(SSHLauncher.java:1178)
    at hudson.plugins.sshslaves.SSHLauncher$2.call(SSHLauncher.java:701)
    at hudson.plugins.sshslaves.SSHLauncher$2.call(SSHLauncher.java:696)
    at java.util.concurrent.FutureTask.run(FutureTask.java:262)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:745)
[06/11/15 09:02:52] Launch failed - cleaning up connection
[06/11/15 09:02:52] [SSH] Connection closed.

本人已验证以下内容：
1.位于/var/lib/jenkins-slave/.ssh的Authorized_keys文件具有正确的主服务器公钥。
1.位于/var/lib/jenkins/.ssh的Authorized_keys文件具有正确的主密钥公钥。

1. Master的私钥和公钥文件位于/var/lib/jenkins/.ssh文件夹和~/.ssh文件夹中。
   我也尝试了“ssh -i .ssh/id_rsa -l jenkins“从主机，但它是要求密码。看起来它不是识别从机。
   主机和从机的.ssh文件夹中都有known_hosts文件，里面有什么数据？
   如何解决这个问题？