这次在Centos 6.3上实现无密码登录，发现怎么样都没能成功，无论怎样，还是需要密码，一下为解决方法
1. 查看ssh 登录的详细信息
ssh -v localhost
发现如下信息：
[shgong@localhost ~]$ ssh -v localhost OpenSSH_5.3p1, OpenSSL 1.0.0-fips 29 Mar 2010 debug1: Reading configuration data /etc/ssh/ssh_config debug1: Applying options for * debug1: Connecting to localhost [::1] port 22. debug1: Connection established. debug1: identity file /home/shgong/.ssh/identity type -1 debug1: identity file /home/shgong/.ssh/id_rsa type 1 debug1: identity file /home/shgong/.ssh/id_dsa type 2 debug1: Remote protocol version 2.0, remote software version OpenSSH_5.3 debug1: match: OpenSSH_5.3 pat OpenSSH* debug1: Enabling compatibility mode for protocol 2.0 debug1: Local version string SSH-2.0-OpenSSH_5.3 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: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP debug1: SSH2_MSG_KEX_DH_GEX_INIT sent debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY debug1: Host 'localhost' is known and matches the RSA host key. debug1: Found key in /home/shgong/.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: SSH2_MSG_SERVICE_REQUEST sent debug1: SSH2_MSG_SERVICE_ACCEPT received debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password debug1: Next authentication method: gssapi-keyex debug1: No valid Key exchange context debug1: Next authentication method: gssapi-with-mic debug1: Unspecified GSS failure. Minor code may provide more information Credentials cache file '/tmp/krb5cc_500' not found debug1: Unspecified GSS failure. Minor code may provide more information Credentials cache file '/tmp/krb5cc_500' not found debug1: Unspecified GSS failure. Minor code may provide more information debug1: Unspecified GSS failure. Minor code may provide more information debug1: Next authentication method: publickey debug1: Trying private key: /home/shgong/.ssh/identity debug1: Offering public key: /home/shgong/.ssh/id_rsa debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password debug1: Offering public key: /home/shgong/.ssh/id_dsa debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password debug1: Next authentication method: password
上面看出了整个登录过程
2. 用root查询系统登录日志
$tail /var/log/secure -n 20
发现如下日志信息：
Sep 15 21:40:06 localhost sudo: shgong : TTY=pts/17 ; PWD=/home/shgong ; USER=root ; COMMAND=/sbin/service sshd restart Sep 15 21:40:06 localhost sshd[4103]: Received signal 15; terminating. Sep 15 21:40:06 localhost sshd[4228]: Server listening on 0.0.0.0 port 22. Sep 15 21:40:06 localhost sshd[4228]: Server listening on :: port 22. Sep 15 21:41:13 localhost sshd[4235]: Authentication refused: bad ownership or modes for file /home/shgong/.ssh/authorized_keys Sep 15 21:41:13 localhost sshd[4235]: Authentication refused: bad ownership or modes for file /home/shgong/.ssh/authorized_keys Sep 15 21:41:13 localhost sshd[4235]: Authentication refused: bad ownership or modes for file /home/shgong/.ssh/authorized_keys Sep 15 21:41:13 localhost sshd[4235]: Authentication refused: bad ownership or modes for file /home/shgong/.ssh/authorized_keys
上面可以看出，无密码登录失败的原因在于authorized_keys的文件权限不对
[shgong@localhost ~]$ ls -lh ~/.ssh/ total 24K -rw-------. 1 shgong shgong 1.5K Sep 15 21:41 authorized_keys -rw-------. 1 shgong shgong 668 Sep 15 21:36 id_dsa -rw-r--r--. 1 shgong shgong 618 Sep 15 21:36 id_dsa.pub -rw-------. 1 shgong shgong 1.7K Sep 15 21:40 id_rsa -rw-r--r--. 1 shgong shgong 410 Sep 15 21:40 id_rsa.pub -rw-r--r--. 1 shgong shgong 391 Sep 15 21:36 known_hosts
3.修改文件权限
[shgong@localhost ~]$ chmod 600 ~/.ssh/authorized_keys
4.重新登录
[shgong@localhost ~]$ ssh -v localhost OpenSSH_5.3p1, OpenSSL 1.0.0-fips 29 Mar 2010 debug1: Reading configuration data /etc/ssh/ssh_config debug1: Applying options for * debug1: Connecting to localhost [::1] port 22. debug1: Connection established. debug1: identity file /home/shgong/.ssh/identity type -1 debug1: identity file /home/shgong/.ssh/id_rsa type 1 debug1: identity file /home/shgong/.ssh/id_dsa type 2 debug1: Remote protocol version 2.0, remote software version OpenSSH_5.3 debug1: match: OpenSSH_5.3 pat OpenSSH* debug1: Enabling compatibility mode for protocol 2.0 debug1: Local version string SSH-2.0-OpenSSH_5.3 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: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP debug1: SSH2_MSG_KEX_DH_GEX_INIT sent debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY debug1: Host 'localhost' is known and matches the RSA host key. debug1: Found key in /home/shgong/.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: SSH2_MSG_SERVICE_REQUEST sent debug1: SSH2_MSG_SERVICE_ACCEPT received debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password debug1: Next authentication method: gssapi-keyex debug1: No valid Key exchange context debug1: Next authentication method: gssapi-with-mic debug1: Unspecified GSS failure. Minor code may provide more information Credentials cache file '/tmp/krb5cc_500' not found debug1: Unspecified GSS failure. Minor code may provide more information Credentials cache file '/tmp/krb5cc_500' not found debug1: Unspecified GSS failure. Minor code may provide more information debug1: Unspecified GSS failure. Minor code may provide more information debug1: Next authentication method: publickey debug1: Trying private key: /home/shgong/.ssh/identity debug1: Offering public key: /home/shgong/.ssh/id_rsa debug1: Server accepts key: pkalg ssh-rsa blen 277 debug1: read PEM private key done: type RSA debug1: Authentication succeeded (publickey). debug1: channel 0: new [client-session] debug1: Requesting no-more-sessions@openssh.com debug1: Entering interactive session. debug1: Sending environment. debug1: Sending env XMODIFIERS = @im=ibus debug1: Sending env LANG = en_US.UTF-8
登录成功！