Ubuntu 17.04 安裝完虛擬機之后，如果想裝ssh軟件進行連接，發現幾乎所有的包都裝不成功。
root@zengxijin-va:/home/zengxijin# 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
報的報錯都是Package ‘xxx’ has no installation candidate。
解決辦法：
（1）備份/etc/apt/sources.list
sudo cp -i /etc/apt/sources.list /etc/apt/sources.list.backup
（2）更新repos
將以下的內容添加到/etc/apt/sources.list（或者將原來的內容清空再添加下面的源）
deb http://archive.ubuntu.com/ubuntu/ trusty main restricted universe multiverse deb http://archive.ubuntu.com/ubuntu/ trusty-security main restricted universe multiverse deb http://archive.ubuntu.com/ubuntu/ trusty-updates main restricted universe multiverse deb http://archive.ubuntu.com/ubuntu/ trusty-proposed main restricted universe multiverse deb http://archive.ubuntu.com/ubuntu/ trusty-backports main restricted universe multiverse
(3)更新：
sudo apt-get update
(4)安裝
sudo apt-get install openssh-server
然后就能安裝成功了，如果遇到版本依賴的沖突，先按照提示安裝對應的依賴版本：如
apt install openssh-client=1:6.6p1-2ubuntu2.10
再正常安裝對應的軟件包就可以了