我上次SSH进入计算引擎实例时，它提示系统重新启动。我重启了。重新启动后，我不再可以ssh了。实例仍在运行，Web服务器仍在工作。我什至可以成功通过身份验证。它比它关闭连接。日志在下面。
ssh -v -i "privatekey" username@hostname
OpenSSH_7.2p2 Ubuntu-4ubuntu2.4, OpenSSL 1.0.2g 1 Mar 2016
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug1: Connecting to hostname [ip] port 22.
debug1: Connection established.
debug1: key_load_public: No such file or directory
debug1: identity file [key location] type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/keyfile-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.2p2 Ubuntu-4ubuntu2.4
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.2p2 Ubuntu-4ubuntu2.4
debug1: match: OpenSSH_7.2p2 Ubuntu-4ubuntu2.4 pat OpenSSH* compat 0x04000000
debug1: Authenticating to hostname:22 as 'username'
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: algorithm: curve25519-sha256@libssh.org
debug1: kex: host key algorithm: ecdsa-sha2-nistp256
debug1: kex: server->client cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none
debug1: kex: client->server cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: Server host key
debug1: Host 'hostname' is known and matches the ECDSA host key.
debug1: Found key in /home/username/.ssh/known_hosts:2
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS received
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<rsa-sha2-256,rsa-sha2-512>
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey
debug1: Next authentication method: publickey
debug1: Trying private key: privatekeyfile
Enter passphrase for key 'privatekeyfile':
debug1: Authentication succeeded (publickey).
Authenticated to hostname ([ip]:22).
debug1: channel 0: new [client-session]
debug1: Requesting no-more-sessions@openssh.com
debug1: Entering interactive session.
debug1: pledge: network
debug1: channel 0: free: client-session, nchannels 1
**Connection to hostname closed by remote host.**
**Connection to hostname closed.**
Transferred: sent 2256, received 1380 bytes, in 0.0 seconds
Bytes per second: sent 155684.5, received 95232.6
debug1: Exit status -1