linux下SSH远程连接服务慢解决方案

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1、适用命令及方案如下：
【远程连接及执行命令】
ssh -p22 root@192.168.1.253
ssh -p22 root@192.168.1.253 /sbin/ifconfig
【远程拷贝：推送及拉取】
scp -P22 -r -p /etc root@192.168.1.253:/tmp/
scp -P22 -r -p root@192.168.1.253:/tmp/ /etc
【安全的FTP功能】
sftp -oPort=22 root@192.168.1.253
【无密码验证方案】
例如利用sshkey批量分发文件，执行部署操作。

2、连接慢的主要原因是DNS解析导致
解决方法：

最为常见的原因是因为server的sshd会去DNS查找访问client IP的hostname，如果DNS不可用或者没有相关记录，就会耗费大量时间。
1、在server上/etc/hosts文件中把你本机的IP和hostname加入

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

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UseDNS no # GSSAPI options GSSAPIAuthentication no

    GSSAPIAuthentication参数是用于Kerberos验证的，而对于绝大多数人来说，不可能使用这种验证机制的，所以要注意把他们停掉。

    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。

3、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。

3、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）。

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[iyunv@localhost ~]# ssh -v root@192.168.2.15 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 192.168.2.15 [192.168.2.15] 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 '192.168.2.15 (192.168.2.15)' 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 =======>这里就是提示保存密钥的交互提示。 Warning: Permanently added '192.168.2.15' (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@192.168.2.15's password: =======>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 LANG = en_US.UTF-8 Last login: Tue Sep 24 10:30:02 2013 from 192.168.2.13 在远程连接时如果慢就可以确定卡在哪了。 [iyunv@localhost ~]# ssh -v oldboy@192.168.2.18 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 192.168.2.18 [192.168.2.18] 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 '192.168.2.18' 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。