今天在安装软件的时候出现了Package has no installation candidate的问题，如：
# apt-get install <packagename>
Reading package lists... Done
Building dependency tree... Done
Package aptitude 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 <packagename> has no installation candidate
解决方法如下：
apt-get update apt-get upgrade apt-get install <packagename>
这样就可以正常使用apt-get了～
添加第三方地址：
sudo add-apt-repository "deb http://archive.canonical.com/ lucid partner" sudo apt-get update
如果以上步骤失败，可以试试以下方法：参考（http://unix.stackexchange.com/questions/140119/every-package-has-no-installation-candidate）
1. 修改 /etc/apt/sources.list 前，注释所有行
sudo vim /etc/apt/sources.list
2. 添加以下安装源， 测试可用
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