Linux包安装依赖问题

最近刚着手linux，在安装软件包时发现依赖关系问题，比如我现在机器上的版本较高，而有些需要用低版本的，关于这个问题，网上有相应的方法：

点击打开链接

但是我在安装aptitude就出现了问题：

sudo apt-get install aptitude
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:
The following packages have unmet dependencies:
 aptitude : Depends: libapt-pkg4.10
            Depends: libept1 but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

这样一来通过aptitude改变版本的方式是不行了，后面发现我自己更新了源，采用网上贴出来的源将原有的官方源覆盖了，后来换成官方源就OK了，安装aptitude成功。

源在/etc/apt目录下，文件名为sources.list，亲们对源进行修改一定要记得做好备份哦。