CentOS下SSH遠端連線服務慢解決方案

1、適用命令及方案如下：
【遠端連線及執行命令】
ssh -p22 root@10.0.0.19
ssh -p22 root@10.0.0.19 /sbin/ifconfig
【遠程拷貝：推送及拉取】
scp -P22 -r -p /etc root@10.0.0.19:/tmp/
scp -P22 -r -p root@10.0.0.19:/tmp/ /etc
【安全的FTP功能】
sftp -oPort=22 root@10.0.0.19
【無密碼驗證方案】
例如利用sshkey批量分發檔案，執行部署操作。

2、串連慢的主要原因是DNS解析導致
解決方案：

1、在ssh服務端上更改/etc/ssh/sshd_config檔案中的配置為如下內容：
UseDNS no
# GSSAPI options
GSSAPIAuthentication no
然後，執行/etc/init.d/sshd restart重啟sshd進程使上述配置生效，在串連一般就不慢了。

2、如果還慢的話，檢查ssh服務端上/etc/hosts檔案中，127.0.0.1對應的主機名稱是否和
uname -n的結果一樣，或者把本機ip和hostname(uname -n結果)加入到/etc/hosts裡。

[root@C64~]# uname -nC64[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################

3、利用ssh-v的調試功能尋找慢的原因

其實可以用下面的命令調試為什麼慢的細節（學習這個思路很重要）。

[root@C64~]# ssh -v root@10.0.0.19OpenSSH_5.3p1, OpenSSL 1.0.0-fips 29 Mar 2010debug1: Reading configuration data /etc/ssh/ssh_configdebug1: Applying options for*debug1: Connecting to 10.0.0.19 [10.0.0.19] port 22.debug1: Connection established.debug1: permanently_set_uid: 0/0debug1: identity file /root/.ssh/identity type -1debug1: identity file /root/.ssh/id_rsa type -1debug1: identity file /root/.ssh/id_dsa type -1debug1: Remote protocol version 2.0, remote software version OpenSSH_4.3debug1: match: OpenSSH_4.3 pat OpenSSH_4*debug1: Enabling compatibility mode forprotocol 2.0debug1: Local version string SSH-2.0-OpenSSH_5.3debug1: SSH2_MSG_KEXINIT sentdebug1: SSH2_MSG_KEXINIT receiveddebug1: kex: server->client aes128-ctr hmac-md5 nonedebug1: kex: client->server aes128-ctr hmac-md5 nonedebug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sentdebug1: expecting SSH2_MSG_KEX_DH_GEX_GROUPdebug1: SSH2_MSG_KEX_DH_GEX_INIT sentdebug1: expecting SSH2_MSG_KEX_DH_GEX_REPLYThe 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=======>老男孩老師評：這裡就是提示儲存密鑰的互動提示。Warning: Permanently added '10.0.0.19' (RSA) to the list of known hosts.debug1: ssh_rsa_verify: signature correctdebug1: SSH2_MSG_NEWKEYS sentdebug1: expecting SSH2_MSG_NEWKEYSdebug1: SSH2_MSG_NEWKEYS receiveddebug1: SSH2_MSG_SERVICE_REQUEST sentdebug1: SSH2_MSG_SERVICE_ACCEPT receiveddebug1: Authentications that can continue: publickey,passworddebug1: Next authentication method: publickeydebug1: Trying private key: /root/.ssh/identitydebug1: Trying private key: /root/.ssh/id_rsadebug1: Trying private key: /root/.ssh/id_dsadebug1: Next authentication method: passwordroot@10.0.0.19's password:=======>老男孩老師評：這裡就是提示輸入密碼的互動提示。debug1: Authentication succeeded (password).debug1: channel 0: new [client-session]debug1: Entering interactive session.debug1: Sending environment.debug1: Sending env LANG = en_US.UTF-8Last login: Tue Sep 24 10:30:02 2013 from 10.0.0.18在遠端連線時如果慢就可以確定卡在哪了。[root@C64_A~]# ssh -v oldboy@10.0.0.17OpenSSH_5.3p1, OpenSSL 1.0.0-fips 29 Mar 2010debug1: Reading configuration data /etc/ssh/ssh_configdebug1: Applying options for*debug1: Connecting to 10.0.0.17 [10.0.0.17] port 22.debug1: Connection established.debug1: permanently_set_uid: 0/0debug1: identity file /root/.ssh/identity type -1debug1: identity file /root/.ssh/id_rsa type -1debug1: identity file /root/.ssh/id_dsa type 2debug1: Remote protocol version 2.0, remote software version OpenSSH_5.3debug1: match: OpenSSH_5.3 pat OpenSSH*debug1: Enabling compatibility mode forprotocol 2.0debug1: Local version string SSH-2.0-OpenSSH_5.3debug1: SSH2_MSG_KEXINIT sentdebug1: SSH2_MSG_KEXINIT receiveddebug1: kex: server->client aes128-ctr hmac-md5 nonedebug1: kex: client->server aes128-ctr hmac-md5 nonedebug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sentdebug1: expecting SSH2_MSG_KEX_DH_GEX_GROUPdebug1: SSH2_MSG_KEX_DH_GEX_INIT sentdebug1: expecting SSH2_MSG_KEX_DH_GEX_REPLYdebug1: Host '10.0.0.17'is known and matches the RSA host key.debug1: Found key in/root/.ssh/known_hosts:2debug1: ssh_rsa_verify: signature correctdebug1: SSH2_MSG_NEWKEYS sentdebug1: expecting SSH2_MSG_NEWKEYSdebug1: SSH2_MSG_NEWKEYS receiveddebug1: SSH2_MSG_SERVICE_REQUEST sentdebug1: SSH2_MSG_SERVICE_ACCEPT receiveddebug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,passworddebug1: Next authentication method: gssapi-keyexdebug1: No valid Key exchange contextdebug1: Next authentication method: gssapi-with-mic

上述配置沒配就發現卡到gssapi這。就大概知道是gssapi的問題。

實際上在linux系統最佳化部分就應該最佳化SSH服務的此處。

本文出自 “老男孩linux營運” 部落格，請務必保留此出處http://oldboy.blog.51cto.com/2561410/1300964