修改apt-get和yum为阿里源

apt-get

在使用apt-get update的时候，出现如下错误时：
E: Some index files failed to download, they have been ignored, or old ones used instead.
可以将目录下/var/lib/apt/lists/partial/所有的文件清掉，再次运行apt-get update即可！

自带源在大陆不好，导致无法下载成功

Err http://security.ubuntu.com precise-security Release.gpg    Temporary failure resolving 'security.ubuntu.com'  Err http://cn.archive.ubuntu.com precise InRelease  .......

步骤

1. 首先可以对原文件进行备份
   sudo cp /etc/apt/source.list /etc/apt/source.list.bak

2. 编辑源列表文件（以管理员身份运行）
   sudo vim /etc/apt/source.list

3. 将文件内容删除，替换如下内容

   deb http://mirrors.aliyun.com/ubuntu/ vivid main restricted universe multiversedeb http://mirrors.aliyun.com/ubuntu/ vivid-security main restricted universe multiversedeb http://mirrors.aliyun.com/ubuntu/ vivid-updates main restricted universe multiversedeb http://mirrors.aliyun.com/ubuntu/ vivid-proposed main restricted universe multiversedeb http://mirrors.aliyun.com/ubuntu/ vivid-backports main restricted universe multiversedeb-src http://mirrors.aliyun.com/ubuntu/ vivid main restricted universe multiversedeb-src http://mirrors.aliyun.com/ubuntu/ vivid-security main restricted universe multiversedeb-src http://mirrors.aliyun.com/ubuntu/ vivid-updates main restricted universe multiversedeb-src http://mirrors.aliyun.com/ubuntu/ vivid-proposed main restricted universe multiverse

4、运行sudo apt-get update

5、运行sudo apt-get upgrade

yum

1、备份

mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup

2、下载新的CentOS-Base.repo 到/etc/yum.repos.d/
CentOS 5

wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-5.repo

CentOS 6

wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-6.repo

CentOS 7

wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo

3、之后运行yum makecache生成缓存