ubuntu，我们在使用apt新装软件的时候，会使用官方的网站去下载软件，但是会因为国内的转接点太多，而导致下载的速度非常慢 ，我们可以通过换成一些中间的节点来进行下载，比如阿里源，中科大源，清华源等等，这样的网站，他们会定时和官方的源进行同步和更新，而我们直接同步他们，速度就会比直接同步官方的源快很多，这样能够大大增加我们的下载软件的速度。
一、ubuntu系统更换源
文件存放在apt文件夹内
所以先进入文件夹
cd /etc/apt
在修改之前对文件进行备份
sudo cp sources.list sources.list.bak
对文件进行修改
sudo vi sources.list
二、删除掉sources.list的其他内容，任意选择一种源的内容复制粘贴进去，保存，例如，选择阿里源
2.1阿里源
deb-src http://archive.ubuntu.com/ubuntu xenial main restricted #Added by software-properties deb http://mirrors.aliyun.com/ubuntu/ xenial main restricted deb-src http://mirrors.aliyun.com/ubuntu/ xenial main restricted multiverse universe #Added by software-properties deb http://mirrors.aliyun.com/ubuntu/ xenial-updates main restricted deb-src http://mirrors.aliyun.com/ubuntu/ xenial-updates main restricted multiverse universe #Added by software-properties deb http://mirrors.aliyun.com/ubuntu/ xenial universe deb http://mirrors.aliyun.com/ubuntu/ xenial-updates universe deb http://mirrors.aliyun.com/ubuntu/ xenial multiverse deb http://mirrors.aliyun.com/ubuntu/ xenial-updates multiverse deb http://mirrors.aliyun.com/ubuntu/ xenial-backports main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ xenial-backports main restricted universe multiverse #Added by software-properties deb http://archive.canonical.com/ubuntu xenial partner deb-src http://archive.canonical.com/ubuntu xenial partner deb http://mirrors.aliyun.com/ubuntu/ xenial-security main restricted deb-src http://mirrors.aliyun.com/ubuntu/ xenial-security main restricted multiverse universe #Added by software-properties deb http://mirrors.aliyun.com/ubuntu/ xenial-security universe deb http://mirrors.aliyun.com/ubuntu/ xenial-security multiverse
今天在用apt-get update更新时一直失败，报的错误为”Failed to fetch 404 Not Found”，因为我的镜像改为了mirrors.aliyun.com 我试着ping了一下发现能通，所以就在网上查找了下答案
大部分的解释是因为每个Ubuntu版本都有生命结束周期（EOL）时间；常规的Ubuntu发行版提供18个月的支持，而LTS（长期支持）版本则长达3年（服务器版本）和5年（桌面版本）。当某个Ubuntu版本达到生命结束周期时，其仓库就不能再访问了，你也不能再从Canonical获取任何维护更新和安全补丁。在撰写本文时，Ubuntu 13.04（急切的浣熊）已经达到了它的生命结束周期。
如果你所使用的Ubuntu系统已经被结束生命周期，你就会从apt-get或aptitude得到以下404错误，因为它的仓库已经被遗弃了。
解决方法为讲/etc/apt/sources.list路径下的源替换为旧版本仓库的源。
BUT，我的镜像是阿里云的镜像，貌似没有什么旧版本的路径，我就在/etc/apt/sources.list路径下删除，重新替换为下面的路径
deb http://mirrors.aliyun.com/ubuntu/ trusty main restricted universe multiverse deb http://mirrors.aliyun.com/ubuntu/ trusty-security main restricted universe multiverse deb http://mirrors.aliyun.com/ubuntu/ trusty-updates main restricted universe multiverse deb http://mirrors.aliyun.com/ubuntu/ trusty-proposed main restricted universe multiverse deb http://mirrors.aliyun.com/ubuntu/ trusty-backports main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ trusty main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ trusty-security main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ trusty-updates main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ trusty-proposed main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ trusty-backports main restricted universe multiverse
之后再apt-get就可以了
2.2东北大学源
deb-src http://mirror.neu.edu.cn/ubuntu/ xenial main restricted #Added by software-properties deb http://mirror.neu.edu.cn/ubuntu/ xenial main restricted deb-src http://mirror.neu.edu.cn/ubuntu/ xenial restricted multiverse universe #Added by software-properties deb http://mirror.neu.edu.cn/ubuntu/ xenial-updates main restricted deb-src http://mirror.neu.edu.cn/ubuntu/ xenial-updates main restricted multiverse universe #Added by software-properties deb http://mirror.neu.edu.cn/ubuntu/ xenial universe deb http://mirror.neu.edu.cn/ubuntu/ xenial-updates universe deb http://mirror.neu.edu.cn/ubuntu/ xenial multiverse deb http://mirror.neu.edu.cn/ubuntu/ xenial-updates multiverse deb http://mirror.neu.edu.cn/ubuntu/ xenial-backports main restricted universe multiverse deb-src http://mirror.neu.edu.cn/ubuntu/ xenial-backports main restricted universe multiverse #Added by software-properties deb http://archive.canonical.com/ubuntu xenial partner deb-src http://archive.canonical.com/ubuntu xenial partner deb http://mirror.neu.edu.cn/ubuntu/ xenial-security main restricted deb-src http://mirror.neu.edu.cn/ubuntu/ xenial-security main restricted multiverse universe #Added by software-properties deb http://mirror.neu.edu.cn/ubuntu/ xenial-security universe deb http://mirror.neu.edu.cn/ubuntu/ xenial-security multiverse
2.3清华大学源
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial main restricted deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-updates main restricted deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial universe deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-updates universe deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial multiverse deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-updates multiverse deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-backports main restricted universe multiverse deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-security main restricted deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-security universe deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-security multiverse
三、更新下载源
sudo apt-get update
四、输入过程中可能会出现的问题
root@ubuntu:/etc/apt# apt-get update
Err:1 http://mirrors.aliyun.com/ubuntu xenial InRelease
Temporary failure resolving 'mirrors.aliyun.com'
Err:2 http://mirrors.aliyun.com/ubuntu xenial-updates InRelease
Temporary failure resolving 'mirrors.aliyun.com'
Err:3 http://mirrors.aliyun.com/ubuntu xenial-backports InRelease
Temporary failure resolving 'mirrors.aliyun.com'
Err:4 http://mirrors.aliyun.com/ubuntu xenial-security InRelease
Temporary failure resolving 'mirrors.aliyun.com'
Err:5 http://archive.canonical.com/ubuntu xenial InRelease
Temporary failure resolving 'archive.canonical.com'
Err:6 http://archive.ubuntu.com/ubuntu xenial InRelease
Temporary failure resolving 'archive.ubuntu.com'
Reading package lists... Done
E: Failed to fetch http://security.ubuntu.com/ubuntu/pool/main/p/perl/perl-base_5.22.1-9ubuntu0.5_amd64.deb Temporary failure resolving 'us.archive.ubuntu.com'
E: Failed to fetch http://security.ubuntu.com/ubuntu/pool/main/p/perl/perl-modules-5.22_5.22.1-9ubuntu0.5_all.deb Temporary failure resolving 'us.archive.ubuntu.com'
E: Failed to fetch http://security.ubuntu.com/ubuntu/pool/main/g/glibc/libc6_2.23-0ubuntu10_amd64.deb Temporary failure resolving 'us.archive.ubuntu.com'
E: Failed to fetch http://security.ubuntu.com/ubuntu/pool/main/d/db5.3/libdb5.3_5.3.28-11ubuntu0.1_amd64.deb Temporary failure resolving 'us.archive.ubuntu.com'
E: Failed to fetch http://us.archive.ubuntu.com/ubuntu/pool/main/z/zlib/zlib1g_1.2.8.dfsg-2ubuntu4.1_amd64.deb Temporary failure resolving 'us.archive.ubuntu.com'
E: Failed to fetch http://us.archive.ubuntu.com/ubuntu/pool/main/i/init-system-helpers/init-system-helpers_1.29ubuntu4_all.deb Temporary failure resolving 'us.archive.ubuntu.com'
E: Failed to fetch http://us.archive.ubuntu.com/ubuntu/pool/main/i/init-system-helpers/init_1.29ubuntu4_amd64.deb Temporary failure resolving 'us.archive.ubuntu.com'
vim /etc/resolv.conf
nameserver 127.0.1.1 nameserver 192.168.23.1 nameserver 221.130.33.52 nameserver 169.95.1.1 nameserver 114.114.114.114
在Ubuntu操作系统中，使用apt-get命令安装所需的开发软件非常方便，但也有不少时候由于链接不上软件源而不能正常安装，于是很多人都会想到使用sudo apt-get update命令来更新软件源，而恰恰这时屋漏偏逢连夜雨，更新命令也不能正常工作，出现大量“Failed to fetch”的错误，出现failed to fetch一般来说是要去更新我们的DNS 再次执行 更新操作
sudo apt-get clean
sudo apt-get update
sudo apt-get upgrade
其他一些命令
sudo apt-get update 更新源 sudo apt-get install package 安装包 sudo apt-get remove package 删除包 sudo apt-cache search package 搜索软件包 sudo apt-cache show package 获取包的相关信息，如说明、大小、版本等 sudo apt-get install package --reinstall 重新安装包 sudo apt-get -f install 修复安装 sudo apt-get remove package --purge 删除包，包括配置文件等 sudo apt-get build-dep package 安装相关的编译环境 sudo apt-get upgrade 更新已安装的包 sudo apt-get dist-upgrade 升级系统 sudo apt-cache depends package 了解使用该包依赖那些包 sudo apt-cache rdepends package 查看该包被哪些包依赖 sudo apt-get source package 下载该包的源代码 sudo apt-get clean && sudo apt-get autoclean 清理无用的包 sudo apt-get check 检查是否有损坏的依赖