使用xshell登录CentOS7，不能登录，使用另外一台Linux主机，telent 22端口是同的，ssh连接报以下错误：
Read from socket failed: Connection reset by peer
查看不能登录主机的日志
# cat /var/log/messages
Dec 15 19:38:27 localhost dbus-daemon: dbus[874]: [system] Successfully activated service ‘org.freedesktop.nm_dispatcher‘
Dec 15 19:38:27 localhost systemd: Started Network Manager Script Dispatcher Service.
Dec 15 19:38:27 localhost nm-dispatcher: Dispatching action ‘dhcp4-change‘ for eno16777736
Dec 15 19:38:33 localhost sshd[3125]: error: Could not load host key: /etc/ssh/ssh_host_rsa_key
Dec 15 19:38:33 localhost sshd[3125]: error: Could not load host key: /etc/ssh/ssh_host_ecdsa_key
Dec 15 19:38:33 localhost sshd[3125]: error: Could not load host key: /etc/ssh/ssh_host_ed25519_key
Dec 15 19:39:42 localhost sshd[3127]: error: Could not load host key: /etc/ssh/ssh_host_rsa_key
Dec 15 19:39:42 localhost sshd[3127]: error: Could not load host key: /etc/ssh/ssh_host_ecdsa_key
Dec 15 19:39:42 localhost sshd[3127]: error: Could not load host key: /etc/ssh/ssh_host_ed25519_key
Dec 15 19:44:56 localhost sshd[3136]: error: Could not load host key: /etc/ssh/ssh_host_ecdsa_key
Dec 15 19:44:56 localhost sshd[3136]: error: Could not load host key: /etc/ssh/ssh_host_ed25519_key
Dec 15 19:47:03 localhost sshd[3138]: error: Could not load host key: /etc/ssh/ssh_host_ecdsa_key
Dec 15 19:47:03 localhost sshd[3138]: error: Could not load host key: /etc/ssh/ssh_host_ed25519_key
找到问题所在，用如下命令
ssh-keygen -t dsa -P ‘‘ -f /etc/ssh/ssh_host_dsa_key
ssh-keygen -t rsa -P ‘‘ -f /etc/ssh/ssh_host_rsa_key
分别把这两个密钥生成就可以正常启动和使用 ssh了 。到此问题就解决完了。
service ssh restart
重启下服务，这个时候就可以连接了。
总结：遇到问题，不要手足无措，首先看看系统提示和日志，好好分析以下。不行立马百度或Google。