问题:
今天在ubuntu下下载redis，执行sudo apt-get update时出现以下错误
Err http://security.ubuntu.com precise-security InRelease
Err http://security.ubuntu.com precise-security Release.gpg
Temporary failure resolving 'security.ubuntu.com'
Err http://cn.archive.ubuntu.com precise InRelease
Err http://cn.archive.ubuntu.com precise-updates InRelease
Err http://cn.archive.ubuntu.com precise-backports InRelease
Err http://cn.archive.ubuntu.com precise Release.gpg
Temporary failure resolving 'cn.archive.ubuntu.com'
Err http://cn.archive.ubuntu.com precise-updates Release.gpg
Temporary failure resolving 'cn.archive.ubuntu.com'
Err http://cn.archive.ubuntu.com precise-backports Release.gpg
Temporary failure resolving 'cn.archive.ubuntu.com'
Reading package lists... Done
W: Failed to fetch http://cn.archive.ubuntu.com/ubuntu/dists/precise/InRelease
W: Failed to fetch http://cn.archive.ubuntu.com/ubuntu/dists/precise-updates/InRelease
W: Failed to fetch http://cn.archive.ubuntu.com/ubuntu/dists/precise-backports/InRelease
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/precise-security/InRelease
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/precise-security/Release.gpg Temporary failure resolving 'security.ubuntu.com'
W: Failed to fetch http://cn.archive.ubuntu.com/ubuntu/dists/precise/Release.gpg Temporary failure resolving 'cn.archive.ubuntu.com'
W: Failed to fetch http://cn.archive.ubuntu.com/ubuntu/dists/precise-updates/Release.gpg Temporary failure resolving 'cn.archive.ubuntu.com'
W: Failed to fetch http://cn.archive.ubuntu.com/ubuntu/dists/precise-backports/Release.gpg Temporary failure resolving 'cn.archive.ubuntu.com'
W: Some index files failed to download. They have been ignored, or old ones used instead.
解决方法:
1.首先修改/etc/apt/sources.list下的镜像源，建议换成阿里镜像源，也可以换成其他的，配置如下:
deb http://mirrors.aliyun.com/ubuntu/ raring main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ raring-security main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ raring-updates main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ raring-proposed main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ raring-backports main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ raring main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ raring-security main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ raring-updates main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ raring-proposed main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ raring-backports main restricted universe multiverse
2.换了之后发现仍然报错，有可能是DNS没配置好，在/etc/resolv.conf文件后添加:
nameserver 127.0.1.1
#阿里云的DNS服务器
nameserver 223.5.5.5
nameserver 223.6.6.6
3.执行sudo apt-get update就正常工作了