使用 Ubuntu 14.04 系统在安装mysql-server时出现报错信息，如下所示：

　　eading 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:

　　mysql-server : Depends: mysql-server-5.5 but it is not going to be instaed

　　E: Unable to correct problems, you have held broken packages.

　　可看到报错是无法解决mysql-server安装时的依赖关系而导致的。

　　因为用户是使用apt-get的方式安装的，那么这种安装方式通常是能够自动解决依赖关系。

　　解决思路：

　　因为系统自带的安装源无法解决安装包依赖问题，更换为新的安装源，解决包依赖问题，安装软件。

　　解决方法：

　　方法一：

　　1.通过wget http://oss.aliyuncs.com/aliyunecs/update_source.tgz 下载update_source的压缩包。

　　2.tar xvf update_source.tgz解压后予执行权限 chmod 777 update_source.sh。

　　3.执行该脚本./update_source.sh进行自动变更源操作。

　　方法二：

　　cp -a /etc/apt/source.list /etc/apt/source.list.bak //备份/etc/apt/source.list文件

　　vim /etc/apt/source.list

　　在最前面添加一下内容

　　deb http://mirrors.aliyun.com/ubuntu/ precise main restricted universe multiverse

　　deb http://mirrors.aliyun.com/ubuntu/ precise-security main restricted universe multiverse

　　deb http://mirrors.aliyun.com/ubuntu/ precise-updates main restricted universe multiverse

　　deb http://mirrors.aliyun.com/ubuntu/ precise-proposed main restricted universe multiverse

　　deb http://mirrors.aliyun.com/ubuntu/ precise-backports main restricted universe multiverse

　　deb-src http://mirrors.aliyun.com/ubuntu/ precise main restricted universe multiverse

　　deb-src http://mirrors.aliyun.com/ubuntu/ precise-security main restricted universe multiverse

　　deb-src http://mirrors.aliyun.com/ubuntu/ precise-updates main restricted universe multiverse

　　deb-src http://mirrors.aliyun.com/ubuntu/ precise-proposed main restricted universe multiverse

　　deb-src http://mirrors.aliyun.com/ubuntu/ precise-backports main restricted universe multiverse

　　apt-get update //更新一下列表