Ubuntu 17.04 安装完虚拟机之后，如果想装ssh软件进行连接，发现几乎所有的包都装不成功。

root@zengxijin-va:/home/zengxijin# apt-get install openssh-serverReading package lists... DoneBuilding dependency tree       Reading state information... DonePackage openssh-server is not available, but is referred to by another package.This may mean that the package is missing, has been obsoleted, oris only available from another sourceE: Package 'openssh-server' has no installation candidate

　　报的报错都是Package ‘xxx’ has no installation candidate。 

解决办法： 

（1）备份/etc/apt/sources.list

sudo cp -i /etc/apt/sources.list /etc/apt/sources.list.backup

（2）更新repos 

将以下的内容添加到/etc/apt/sources.list（或者将原来的内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)安装

sudo apt-get install openssh-server

　　然后就能安装成功了，如果遇到版本依赖的冲突，先按照提示安装对应的依赖版本：如

apt install openssh-client=1:6.6p1-2ubuntu2.10

　　再正常安装对应的软件包就可以了