$sduo apt-get install openssh-server Reading package lists… Done Building dependency tree Reading state information… Done Package openssh-server is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source E: Package openssh-server has no installation candidate
執行:sudo apt-get update 也提示更新失敗，或者無內容可更新。
解決方案：sudo vim /etc/network/interfaces修改ip，重啟。
執行：sudo apt-get update
問題解決：
http://blog.sina.com.cn/s/blog_3e28c8a50101cax0.html