本文主要向大家介绍了如何解决Linux系统运维下SSH远程连接服务卡慢，通过具体的步骤向大家展现，希望对大家学习Linux系统运维有所帮助。

连接慢的主要原因是DNS解析导致

解决方法：

1、在ssh服务端上更改/etc/ssh/sshd_config文件中的配置为如下内容：

UseDNS no# GSSAPI options

GSSAPIAuthentication no

然后，执行/etc/init.d/sshd restart重启sshd进程使上述配置生效，在连接一般就不慢了。

2、如果还慢的话，检查ssh服务端上/etc/hosts文件中，127.0.0.1对应的主机名是否和 uname -n的结果一样，或者把本机ip和hostname(uname -n结果)加入到/etc/hosts里。

[root@C64 ~]# uname -n

C64

[root@C64 ~]# cat /etc/hosts#modi by oldboy 11:12 2013/9/24127.0.0.1   C64 localhost localhost.localdomain localhost4 localhost4.localdomain4

::1         localhost localhost.localdomain localhost6 localhost6.localdomain610.0.0.18   C64################

利用ssh -v的调试功能查找慢的原因

其实可以用下面的命令调试为什么慢的细节（学习这个思路很重要）。

[root@C64 ~]# ssh -v root@10.0.0.19

OpenSSH_5.3p1, OpenSSL 1.0.0-fips 29 Mar 2010

debug1: Reading configuration data /etc/ssh/ssh_config

debug1: Applying options for *

debug1: Connecting to 10.0.0.19 [10.0.0.19] port 22.

debug1: Connection established.

debug1: permanently_set_uid: 0/0

debug1: identity file /root/.ssh/identity type -1

debug1: identity file /root/.ssh/id_rsa type -1

debug1: identity file /root/.ssh/id_dsa type -1

debug1: Remote protocol version 2.0, remote software version OpenSSH_4.3

debug1: match: OpenSSH_4.3 pat OpenSSH_4*

debug1: Enabling compatibility mode for protocol 2.0

debug1: Local version string SSH-2.0-OpenSSH_5.3

debug1: SSH2_MSG_KEXINIT sent

debug1: SSH2_MSG_KEXINIT received

debug1: kex: server->client aes128-ctr hmac-md5 none

debug1: kex: client->server aes128-ctr hmac-md5 none

debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent

debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP

debug1: SSH2_MSG_KEX_DH_GEX_INIT sent

debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY

The authenticity of host '10.0.0.19 (10.0.0.19)' can't be established.

RSA key fingerprint is ca:18:42:76:0e:5a:1c:7d:ef:fc:24:75:80:11:ad:f9.

Are you sure you want to continue connecting (yes/no)? yes

=======>老男孩老师评：这里就是提示保存密钥的交互提示。

Warning: Permanently added '10.0.0.19' (RSA) to the list of known hosts.

debug1: ssh_rsa_verify: signature correct

debug1: SSH2_MSG_NEWKEYS sent

debug1: expecting SSH2_MSG_NEWKEYS

debug1: SSH2_MSG_NEWKEYS received

debug1: SSH2_MSG_SERVICE_REQUEST sent

debug1: SSH2_MSG_SERVICE_ACCEPT received

debug1: Authentications that can continue: publickey,password

debug1: Next authentication method: publickey

debug1: Trying private key: /root/.ssh/identity

debug1: Trying private key: /root/.ssh/id_rsa

debug1: Trying private key: /root/.ssh/id_dsa

debug1: Next authentication method: password

root@10.0.0.19's password:

=======>老男孩老师评：这里就是提示输入密码的交互提示。

debug1: Authentication succeeded (password).

debug1: channel 0: new [client-session]

debug1: Entering interactive session.

debug1: Sending environment.

debug1: Sending env.UTF-8

Last login: Tue Sep 24 10:30:02 2013 from 10.0.0.18

在远程连接时如果慢就可以确定卡在哪了。

[root@C64_A ~]# ssh -v oldboy@10.0.0.17

OpenSSH_5.3p1, OpenSSL 1.0.0-fips 29 Mar 2010

debug1: Reading configuration data /etc/ssh/ssh_config

debug1: Applying options for *

debug1: Connecting to 10.0.0.17 [10.0.0.17] port 22.

debug1: Connection established.

debug1: permanently_set_uid: 0/0

debug1: identity file /root/.ssh/identity type -1

debug1: identity file /root/.ssh/id_rsa type -1

debug1: identity file /root/.ssh/id_dsa type 2

debug1: Remote protocol version 2.0, remote software version OpenSSH_5.3

debug1: match: OpenSSH_5.3 pat OpenSSH*

debug1: Enabling compatibility mode for protocol 2.0

debug1: Local version string SSH-2.0-OpenSSH_5.3

debug1: SSH2_MSG_KEXINIT sent

debug1: SSH2_MSG_KEXINIT received

debug1: kex: server->client aes128-ctr hmac-md5 none

debug1: kex: client->server aes128-ctr hmac-md5 none

debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent

debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP

debug1: SSH2_MSG_KEX_DH_GEX_INIT sent

debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY

debug1: Host '10.0.0.17' is known and matches the RSA host key.

debug1: Found key in /root/.ssh/known_hosts:2

debug1: ssh_rsa_verify: signature correct

debug1: SSH2_MSG_NEWKEYS sent

debug1: expecting SSH2_MSG_NEWKEYS

debug1: SSH2_MSG_NEWKEYS received

debug1: SSH2_MSG_SERVICE_REQUEST sent

debug1: SSH2_MSG_SERVICE_ACCEPT received

debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password

debug1: Next authentication method: gssapi-keyex

debug1: No valid Key exchange context

debug1: Next authentication method: gssapi-with-mic

上述配置没配就发现卡到gssapi这。就大概知道是gssapi的问题。

实际上在linux系统优化部分就应该优化SSH服务的此处。

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