阿里云有些包无法更新，修改

新买的阿里云服务器无法下载php7.0的一系列拓展,发现是源有问题,需要更换源,首先备份

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

接着讲source.list中的源全部注释掉,粘贴进以下源,就可以下载PHP7.0的拓展了

deb http://mirrors.cloud.aliyuncs.com/ubuntu/ xenial main restricted universe multiverse

deb http://mirrors.cloud.aliyuncs.com/ubuntu/ xenial-security main restricted universe multiverse

deb http://mirrors.cloud.aliyuncs.com/ubuntu/ xenial-updates main restricted universe multiverse

deb http://mirrors.cloud.aliyuncs.com/ubuntu/ xenial-proposed main restricted universe multiverse

deb http://mirrors.cloud.aliyuncs.com/ubuntu/ xenial-backports main restricted universe multiverse

deb-src http://mirrors.cloud.aliyuncs.com/ubuntu/ xenial main restricted universe multiverse

deb-src http://mirrors.cloud.aliyuncs.com/ubuntu/ xenial-security main restricted universe multiverse

deb-src http://mirrors.cloud.aliyuncs.com/ubuntu/ xenial-updates main restricted universe multiverse

deb-src http://mirrors.cloud.aliyuncs.com/ubuntu/ xenial-proposed main restricted universe multiverse

deb-src http://mirrors.cloud.aliyuncs.com/ubuntu/ xenial-backports main restricted universe multiverse