黃昏的甘蔗

近期遇到一台以SSH登入的 CentOS 主機，其帳號密碼正確的情況下，輸入帳密後還得等好一段時間，才會出現 prompt # ，怎麼會這麼慢呢？上網查詢一下可能是 GSSAPI 跟 DNS 查詢的問題。

解決方法：
修改 sudo vi /etc/ssh/sshd_config

1. 將 GSSAPIAuthentication yes
改成
GSSAPIAuthentication no

2. 將 #UseDNS yes
改成
UseDNS no

3. 重新啟動 sshd 服務
sudo service sshd restart

搞定收工........

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GSSAPI 是 Generic Security Service Application Program Interface，
The GSSAPI is a generic API for doing client-server authentication. The motivation behind it is that every security system has it's own API, and the effort involved with adding different security systems to applications is extremely difficult with the variance between security APIs. However, with a common API, application vendors could write to the generic API and it could work with any number of security systems.
詳細請參考：http://en.wikipedia.org/wiki/Generic_Security_Services_Application_Program_Interface 
https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Virtualization/3.0/html/Technical_Reference_Guide/sect-Technical_Reference_Guide-Directory_Services-Remote_Authentication_Using_GSSAPI.html 

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