Ubuntu上安装软件常用方法为： sudo apt-get install <Package name>
执行该命令时，遇到过两个问题，耽误了很多时间，现整理一下，多亏了万能的Internet，和各路大神的blog。才使得问题解决：
1、 "0% [Waiting for headers]"
出现原因：可能是之前你在安装时按了Ctrl+C。
解决办法：
sudo rm /var/cache/apt/archives/partial/ -rf
2、sudo apt-get update 时 有的更新失败，比如打印：
Fetch failed hash sum mismatch 或者在sudo apt-get install <Package name>时出现类似如下的错误：
root@ubuntu:/# apt-get install libsdl1.2-dev
Reading package lists... Done
Building dependency tree
Reading state information... Done
Note, selecting 'libsdl1.2-dev' instead of 'libsdl-dev'
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:
libsdl1.2-dev : Depends: libpulse-dev but it is not going to be installed
E: Unable to correct problems, you have held broken packages.
出现原因：可能是网络不好吧，在Ubuntu 14.04上遇到的这个问题
我是通过换源（sources）解决的：
可以通过命令行解决（可参考
http://www.cnblogs.com/zhangpengshou/p/3591387.html
）;cd /etc/apt/ 该目录下随便摸索吧
我是通过在system settings 解决的，操作如下图所示：
选择System Settings -> Software & Updates -> 修改Downloads from ->可以选择中国的（我选了阿里云）-> close
可能根据提示需要重新reload，更新就行了。或者重新 sudo apt-get update。问题解决。
