SSH 一连接上就断开
调试信息输出：
debug1: key_parse_private2: missing begin marker
debug1: read PEM private key done: type RSA
debug1: private host key: #0 type 1 RSA
debug1: key_parse_private2: missing begin marker
debug1: read PEM private key done: type DSA
debug1: private host key: #1 type 2 DSA
debug1: key_parse_private2: missing begin marker
debug1: read PEM private key done: type ECDSA
debug1: private host key: #2 type 3 ECDSA
debug1: rexec_argv[0]='/usr/sbin/sshd'
debug1: rexec_argv[1]='-d'
Set /proc/self/oom_score_adj from 0 to -1000
debug1: Bind to port 22 on 0.0.0.0.
Server listening on 0.0.0.0 port 22.
debug1: Bind to port 22 on ::.
Server listening on :: port 22.
debug1: Server will not fork when running in debugging mode.
debug1: rexec start in 5 out 5 newsock 5 pipe -1 sock 8
debug1: inetd sockets after dupping: 3, 3
Connection from 118.11.11.11 port 40989 on 172.11.11.11 port 22
debug1: Client protocol version 2.0; client software version SecureCRT_7.0.0 (x64 build 326) SecureCRT
debug1: no match: SecureCRT_7.0.0 (x64 build 326) SecureCRT
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_6.6.1p1 Ubuntu-2ubuntu2
debug1: permanently_set_uid: 110/65534 [preauth]
debug1: list_hostkey_types: ssh-rsa,ssh-dss,ecdsa-sha2-nistp256 [preauth]
debug1: SSH2_MSG_KEXINIT sent [preauth]
debug1: SSH2_MSG_KEXINIT received [preauth]
debug1: kex: client->server aes256-ctr hmac-sha1 none [preauth]
debug1: kex: server->client aes256-ctr hmac-sha1 none [preauth]
debug1: expecting SSH2_MSG_KEXDH_INIT [preauth]
debug1: SSH2_MSG_NEWKEYS sent [preauth]
debug1: expecting SSH2_MSG_NEWKEYS [preauth]
debug1: SSH2_MSG_NEWKEYS received [preauth]
debug1: KEX done [preauth]
debug1: userauth-request for user root service ssh-connection method none [preauth]
debug1: attempt 0 failures 0 [preauth]
debug1: PAM: initializing for "root"
debug1: PAM: setting PAM_RHOST to "118.*****。**。**"
debug1: PAM: setting PAM_TTY to "ssh"
解决方法：
找到下面文件，注释掉这一行
Just comment this line in file "/etc/pam.d/sshd":
session required pam_loginuid.so
