最近我们将 sftp 服务器从 ubuntu 14.04 切换到 16.04，从那时起，我的一个远程客户端就无法连接。我尝试了不同的方法，并且意识到了遗留问题，并在 sshd_config 中添加了一些遗留的 KEX 选项，但客户端仍然无法连接。有人对问题可能是什么还有其他想法吗？我在下面发布了一些清理过的调试输出。
Jul 11 11:49:05 etl-hub-sftp-0 sshd[20079]: debug1: Forked child 25871.
Jul 11 11:49:05 etl-hub-sftp-0 sshd[25871]: debug1: Set /proc/self/oom_score_adj to 0
Jul 11 11:49:05 etl-hub-sftp-0 sshd[25871]: debug1: rexec start in 5 out 5 newsock 5 pipe 7 sock 8
Jul 11 11:49:05 etl-hub-sftp-0 sshd[25871]: debug1: inetd sockets after dupping: 3, 3
Jul 11 11:49:05 etl-hub-sftp-0 sshd[25871]: Connection from xxx.xxx.xxx.xxx port 51284 on yyy.yyy.yyy.yyy port 22
Jul 11 11:49:05 etl-hub-sftp-0 sshd[25871]: debug1: Client protocol version 2.0; client software version maverick_legacy_1.6.0
Jul 11 11:49:05 etl-hub-sftp-0 sshd[25871]: debug1: no match: maverick_legacy_1.6.0
Jul 11 11:49:05 etl-hub-sftp-0 sshd[25871]: debug1: Enabling compatibility mode for protocol 2.0
Jul 11 11:49:05 etl-hub-sftp-0 sshd[25871]: debug1: Local version string SSH-2.0-OpenSSH_7.2p2 Ubuntu-4ubuntu2.8
Jul 11 11:49:05 etl-hub-sftp-0 sshd[25871]: debug1: permanently_set_uid: 108/65534 [preauth]
Jul 11 11:49:05 etl-hub-sftp-0 sshd[25871]: debug1: list_hostkey_types: ssh-rsa,rsa-sha2-512,rsa-sha2-256,ecdsa-sha2-nistp256,ssh-ed25519 [preauth]
Jul 11 11:49:05 etl-hub-sftp-0 sshd[25871]: debug1: SSH2_MSG_KEXINIT sent [preauth]
Jul 11 11:49:05 etl-hub-sftp-0 sshd[25871]: debug1: SSH2_MSG_KEXINIT received [preauth]
Jul 11 11:49:05 etl-hub-sftp-0 sshd[25871]: debug1: kex: algorithm: diffie-hellman-group-exchange-sha256 [preauth]
Jul 11 11:49:05 etl-hub-sftp-0 sshd[25871]: debug1: kex: host key algorithm: ssh-rsa [preauth]
Jul 11 11:49:05 etl-hub-sftp-0 sshd[25871]: debug1: kex: client->server cipher: aes128-ctr MAC: hmac-sha2-256 compression: none [preauth]
Jul 11 11:49:05 etl-hub-sftp-0 sshd[25871]: debug1: kex: server->client cipher: aes128-ctr MAC: hmac-sha2-256 compression: none [preauth]
Jul 11 11:49:05 etl-hub-sftp-0 sshd[25871]: debug1: expecting SSH2_MSG_KEX_DH_GEX_REQUEST [preauth]
Jul 11 11:49:05 etl-hub-sftp-0 sshd[25871]: error: kex protocol error: type 30 seq 1 [preauth]
Jul 11 11:49:05 etl-hub-sftp-0 sshd[25871]: error: Received disconnect from xxx.xxx.xxx.xxx port 51284:3: Expected SSH_MSG_KEX_GEX_GROUP [preauth]
Jul 11 11:49:05 etl-hub-sftp-0 sshd[25871]: Disconnected from xxx.xxx.xxx.xxx port 51284 [preauth]
Jul 11 11:49:05 etl-hub-sftp-0 sshd[25871]: debug1: do_cleanup [preauth]
Jul 11 11:49:05 etl-hub-sftp-0 sshd[25871]: debug1: monitor_read_log: child log fd closed
Jul 11 11:49:05 etl-hub-sftp-0 sshd[25871]: debug1: do_cleanup
Jul 11 11:49:05 etl-hub-sftp-0 sshd[25871]: debug1: Killing privsep child 25872
Jul 11 11:49:05 etl-hub-sftp-0 sshd[25871]: debug1: audit_event: unhandled event 12