ubuntu，我們在使用apt新裝軟件的時候，會使用官方的網站去下載軟件，但是會因為國內的轉接點太多，而導致下載的速度非常慢 ，我們可以通過換成一些中間的節點來進行下載，比如阿里源，中科大源，清華源等等，這樣的網站，他們會定時和官方的源進行同步和更新，而我們直接同步他們，速度就會比直接同步官方的源快很多，這樣能夠大大增加我們的下載軟件的速度。
一、ubuntu系統更換源
文件存放在apt文件夾內
所以先進入文件夾
cd /etc/apt
在修改之前對文件進行備份
sudo cp sources.list sources.list.bak
對文件進行修改
sudo vi sources.list
二、刪除掉sources.list的其他內容，任意選擇一種源的內容復制粘貼進去，保存，例如，選擇阿里源
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更新時一直失敗，報的錯誤為”Failed to fetch 404 Not Found”，因為我的鏡像改為了mirrors.aliyun.com 我試着ping了一下發現能通，所以就在網上查找了下答案
大部分的解釋是因為每個Ubuntu版本都有生命結束周期（EOL）時間；常規的Ubuntu發行版提供18個月的支持，而LTS（長期支持）版本則長達3年（服務器版本）和5年（桌面版本）。當某個Ubuntu版本達到生命結束周期時，其倉庫就不能再訪問了，你也不能再從Canonical獲取任何維護更新和安全補丁。在撰寫本文時，Ubuntu 13.04（急切的浣熊）已經達到了它的生命結束周期。
如果你所使用的Ubuntu系統已經被結束生命周期，你就會從apt-get或aptitude得到以下404錯誤，因為它的倉庫已經被遺棄了。
解決方法為講/etc/apt/sources.list路徑下的源替換為舊版本倉庫的源。
BUT，我的鏡像是阿里雲的鏡像，貌似沒有什么舊版本的路徑，我就在/etc/apt/sources.list路徑下刪除，重新替換為下面的路徑
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東北大學源
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清華大學源
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、更新下載源
sudo apt-get update
四、輸入過程中可能會出現的問題
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操作系統中，使用apt-get命令安裝所需的開發軟件非常方便，但也有不少時候由於鏈接不上軟件源而不能正常安裝，於是很多人都會想到使用sudo apt-get update命令來更新軟件源，而恰恰這時屋漏偏逢連夜雨，更新命令也不能正常工作，出現大量“Failed to fetch”的錯誤，出現failed to fetch一般來說是要去更新我們的DNS 再次執行 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 安裝包 sudo apt-get remove package 刪除包 sudo apt-cache search package 搜索軟件包 sudo apt-cache show package 獲取包的相關信息，如說明、大小、版本等 sudo apt-get install package --reinstall 重新安裝包 sudo apt-get -f install 修復安裝 sudo apt-get remove package --purge 刪除包，包括配置文件等 sudo apt-get build-dep package 安裝相關的編譯環境 sudo apt-get upgrade 更新已安裝的包 sudo apt-get dist-upgrade 升級系統 sudo apt-cache depends package 了解使用該包依賴那些包 sudo apt-cache rdepends package 查看該包被哪些包依賴 sudo apt-get source package 下載該包的源代碼 sudo apt-get clean && sudo apt-get autoclean 清理無用的包 sudo apt-get check 檢查是否有損壞的依賴