排查ssh建立连接慢的问题记录

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  14/07/2022   09:20.50   /home/mobaxterm   

ssh -v root@192.168.248.215
OpenSSH_7.5p1, OpenSSL 1.0.2o  27 Mar 2018
debug1: Reading configuration data /etc/ssh_config
debug1: /etc/ssh_config line 10: Deprecated option "useroaming"
debug1: Connecting to 192.168.248.215 [192.168.248.215] port 22.
debug1: Connection established.
debug1: key_load_public: No such file or directory
debug1: identity file /home/mobaxterm/.ssh/id_rsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/mobaxterm/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/mobaxterm/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/mobaxterm/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/mobaxterm/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/mobaxterm/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/mobaxterm/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/mobaxterm/.ssh/id_ed25519-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.5
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.4
debug1: match: OpenSSH_7.4 pat OpenSSH* compat 0x04000000
debug1: Authenticating to 192.168.248.215:22 as 'root'
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: algorithm: curve25519-sha256
debug1: kex: host key algorithm: ecdsa-sha2-nistp256
debug1: kex: server->client cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: zlib@openssh.com
debug1: kex: client->server cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: zlib@openssh.com
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:l4rDx6IMQ5RvRMsKIAGVGCSjMYjJkCBP0qrXGIoaApo
debug1: Host '192.168.248.215' is known and matches the ECDSA host key.
debug1: Found key in /home/mobaxterm/.ssh/known_hosts:1
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: rekey after 134217728 blocks
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,gssapi-keyex,gssapi-with-mic,password
debug1: Next authentication method: publickey
debug1: Trying private key: /home/mobaxterm/.ssh/id_rsa
debug1: Trying private key: /home/mobaxterm/.ssh/id_dsa
debug1: Trying private key: /home/mobaxterm/.ssh/id_ecdsa
debug1: Trying private key: /home/mobaxterm/.ssh/id_ed25519
debug1: Next authentication method: password
debug1: Enabling compression at level 6.
debug1: Authentication succeeded (password).
Authenticated to 192.168.248.215 ([192.168.248.215]:22).
debug1: channel 0: new [client-session]
debug1: Requesting no-more-sessions@openssh.com
debug1: Entering interactive session.
debug1: pledge: exec
debug1: client_input_global_request: rtype hostkeys-00@openssh.com want_reply 0
debug1: Requesting X11 forwarding with authentication spoofing.
debug1: Remote: No xauth program; cannot forward with spoofing.
X11 forwarding request failed on channel 0

 

排查过程：

连接ssh时带上-v参数做一下调试

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ssh -v root@192.168.248.215

过程debug时卡在了（等待时间较久）

SSH2_MSG_SERVICE_ACCEPT received

于是求助万能的搜索引擎：

在该路径 /etc/ssh/sshd_config 文件中将 UseDNS 设置为 no

然后重启sshd：

?

1	service sshd restart

试试看效果