问题：$ ssh -T git@github.com
Permission denied (publickey)
解析：
1、可以看出问题出在publickey(公钥)
2、接着ssh -T -v git@github.com 看下具体信息
penSSH_6.1p1 Debian-4, OpenSSL 1.0.1c 10 May 2012
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug1: Connecting to github.com [192.30.252.131] port 22.
debug1: Connection established.
debug1: identity file /home/sunny/.ssh/id_rsa type -1
debug1: identity file /home/sunny/.ssh/id_rsa-cert type -1
debug1: identity file /home/sunny/.ssh/id_dsa type -1
debug1: identity file /home/sunny/.ssh/id_dsa-cert type -1
debug1: identity file /home/sunny/.ssh/id_ecdsa type -1
debug1: identity file /home/sunny/.ssh/id_ecdsa-cert type -1
debug1: Remote protocol version 2.0, remote software version OpenSSH_5.9p1 Debian-5ubuntu1+github5
debug1: match: OpenSSH_5.9p1 Debian-5ubuntu1+github5 pat OpenSSH_5*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_6.1p1 Debian-4
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: server->client aes128-ctr hmac-md5 none
debug1: kex: client->server aes128-ctr hmac-md5 none
debug1: sending SSH2_MSG_KEX_ECDH_INIT
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: RSA 16:27:ac:a5:76:28:2d:36:63:1b:56:4d:eb:df:a6:48
debug1: Host 'github.com' is known and matches the RSA host key.
debug1: Found key in /home/sunny/.ssh/known_hosts:1
debug1: ssh_rsa_verify: signature correct
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: Roaming not allowed by server
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey
debug1: Next authentication method: publickey
debug1: Trying private key: /home/sunny/.ssh/id_rsa
debug1: Trying private key: /home/sunny/.ssh/id_dsa
debug1: Trying private key: /home/sunny/.ssh/id_ecdsa
debug1: No more authentication methods to try.
Permission denied (publickey).
3、可以发现在一下几行出现问题：
debug1: Next authentication method: publickey
debug1: Trying private key: /home/sunny/.ssh/id_rsa
debug1: Trying private key: /home/sunny/.ssh/id_dsa
debug1: Trying private key: /home/sunny/.ssh/id_ecdsa
debug1: No more authentication methods to try.
Permission denied (publickey).
4、发现它一直在查找id_rsa、id_dsa、id_ecdsa这三个文件，然后就不尝试其他了;
5、我们查看下 ~/.ssh文件夹下的文件：ls ~/.ssh
github github.pub ...
这里没有第4步出现的文件，github是创建ssh-key时输入的名字
6、现在我们让~/.ssh文件夹下,还原当初没有改时的名字id_rsa
cp github id_rsa && cp gitbub.pub id_rsa.pub
7、再次尝试连接:ssh -T git@github.com
Hi xxx ! You've successfully authenticated, but GitHub does not provide shell access.成功。
总结：
运用shh -T -v git@github.com查看具体出错信息，再根据信息来调试
转自：http://blog.csdn.net/sunnypotter/article/details/18948053