Ubuntu的官方源对于国内用户来说是比较慢的，可以将它的源换成国内的源，用起来就快很多了。

# Ubuntu server 环境
ubuntu@ubuntu:~$  sudo su -
[ sudo ] password  for ubuntu:

root@ubuntu:~ # uname -r
3.19.0-25-generic
root@DDTSC-Test-01:~ # lsb_release -a
No LSB modules are available.
Distributor ID:    Ubuntu
Description:    Ubuntu 14.04.5 LTS
Release:    14.04
Codename:    trusty
root@ubuntu:~ # ufw status
Status: inactive
root@ubuntu:~ # ufw version
ufw 0.34~rc-0ubuntu2
Copyright 2008-2012 Canonical Ltd.

# Ubuntu自带的源
root@ubuntu:~ # grep -E -v '^#|^$' /etc/apt/sources.list
deb http: //us .archive.ubuntu.com /ubuntu/ trusty main restricted
deb-src http: //us .archive.ubuntu.com /ubuntu/ trusty main restricted
deb http: //us .archive.ubuntu.com /ubuntu/ trusty-updates main restricted
deb-src http: //us .archive.ubuntu.com /ubuntu/ trusty-updates main restricted
deb http: //us .archive.ubuntu.com /ubuntu/ trusty universe
deb-src http: //us .archive.ubuntu.com /ubuntu/ trusty universe
deb http: //us .archive.ubuntu.com /ubuntu/ trusty-updates universe
deb-src http: //us .archive.ubuntu.com /ubuntu/ trusty-updates universe
deb http: //us .archive.ubuntu.com /ubuntu/ trusty multiverse
deb-src http: //us .archive.ubuntu.com /ubuntu/ trusty multiverse
deb http: //us .archive.ubuntu.com /ubuntu/ trusty-updates multiverse
deb-src http: //us .archive.ubuntu.com /ubuntu/ trusty-updates multiverse
deb http: //us .archive.ubuntu.com /ubuntu/ trusty-backports main restricted universe multiverse
deb-src http: //us .archive.ubuntu.com /ubuntu/ trusty-backports main restricted universe multiverse
deb http: //security .ubuntu.com /ubuntu trusty-security main restricted
deb-src http: //security .ubuntu.com /ubuntu trusty-security main restricted
deb http: //security .ubuntu.com /ubuntu trusty-security universe
deb-src http: //security .ubuntu.com /ubuntu trusty-security universe
deb http: //security .ubuntu.com /ubuntu trusty-security multiverse
deb-src http: //security .ubuntu.com /ubuntu trusty-security multiverse

# 备份源列表
root@ubuntu:~ # mv /etc/apt/sources.list /etc/apt/sources.list_bak

# 阿里云源
root@ubuntu:~ # vim /etc/apt/sources.list
deb https: //mirrors .aliyun.com /ubuntu/ trusty main restricted universe multiverse
deb-src https: //mirrors .aliyun.com /ubuntu/ trusty main restricted universe multiverse
deb https: //mirrors .aliyun.com /ubuntu/ trusty-security main restricted universe multiverse
deb-src https: //mirrors .aliyun.com /ubuntu/ trusty-security main restricted universe multiverse
deb https: //mirrors .aliyun.com /ubuntu/ trusty-updates main restricted universe multiverse
deb-src https: //mirrors .aliyun.com /ubuntu/ trusty-updates main restricted universe multiverse
deb https: //mirrors .aliyun.com /ubuntu/ trusty-backports main restricted universe multiverse
deb-src https: //mirrors .aliyun.com /ubuntu/ trusty-backports main restricted universe multiverse
## Not recommended
# deb https://mirrors.aliyun.com/ubuntu/ trusty-proposed main restricted universe multiverse
# deb-src https://mirrors.aliyun.com/ubuntu/ trusty-proposed main restricted universe multiverse

以上内容的带有词含义解析：
　　proposed　　预发布软件源，不建议启用
　　deb-src　　　　　　源码

# 更新源
root@ubuntu:~ # apt-get update
...
...若出现以下错误提示
... "Hash Sum mismatch"

　解决办法：
　　 sudo rm -rf  /var/lib/apt/lists/ *　　　　　　 # 删掉/var/lib/apt/lists 这个目录下的东西
　　 sudo mkdir /var/lib/apt/lists/partial 　　　 # 新建相应文件夹
　　 sudo apt-get update　　　　　　　　　　　　　 # 重新update

# 更新软件
root@ubuntu:~ # apt-get upgrade
...
...若出现以下错误提示
subprocess dpkg-deb --control returned error  exit status 2
E: Sub-process  /usr/bin/dpkg returned an error code (1)

　解决办法：
　　 cd /var/lib/dpkg/
　　 sudo mv info/ info_bak           # 现将info文件夹更名
　　 sudo mkdir info                  # 再新建一个新的info文件夹
　　 sudo apt-get update              # 更新
　　 sudo apt-get -f  install # 修复
　　 sudo mv info/* info_bak/         # 执行完上一步操作后会在新的info文件夹下生成一些文件，现将这些文件全部移到info_bak文件夹下
　　 sudo rm -rf info                 # 把自己新建的info文件夹删掉
　　 sudo mv info_bak info            # 把以前的info文件夹重新改回名

apt-get upgrade和dist-upgrade的差别:
　　upgrade：系统将现有的Package升级,如果有相依性的问题,而此相依性需要安装其它新的Package或影响到其它Package的相依性时,此Package就不会被升级,会保留下来.
　　dist-upgrade：可以聪明的解决相依性的问题,如果有相依性问题,需要安装/移除新的Package,就会试着去安装/移除它. (所以通常这个会被认为是有点风险的升级)

---------------------------------------------------------------------------------------------
# 清华源
deb http: //mirrors .tuna.tsinghua.edu.cn /ubuntu/ focal main restricted
deb http: //mirrors .tuna.tsinghua.edu.cn /ubuntu/ focal-updates main restricted
deb http: //mirrors .tuna.tsinghua.edu.cn /ubuntu/ focal universe
deb http: //mirrors .tuna.tsinghua.edu.cn /ubuntu/ focal-updates universe
deb http: //mirrors .tuna.tsinghua.edu.cn /ubuntu/ focal multiverse
deb http: //mirrors .tuna.tsinghua.edu.cn /ubuntu/ focal-updates multiverse
deb http: //mirrors .tuna.tsinghua.edu.cn /ubuntu/ focal-backports main restricted universe multiverse
deb http: //mirrors .tuna.tsinghua.edu.cn /ubuntu/ focal-security main restricted
deb http: //mirrors .tuna.tsinghua.edu.cn /ubuntu/ focal-security universe
deb http: //mirrors .tuna.tsinghua.edu.cn /ubuntu/ focal-security multiverse
---------------------------------------------------------------------------------------------
# 中科大源
deb https: //mirrors .ustc.edu.cn /ubuntu/ focal main restricted universe multiverse
deb-src https: //mirrors .ustc.edu.cn /ubuntu/ focal main restricted universe multiverse
deb https: //mirrors .ustc.edu.cn /ubuntu/ focal-updates main restricted universe multiverse
deb-src https: //mirrors .ustc.edu.cn /ubuntu/ focal-updates main restricted universe multiverse
deb https: //mirrors .ustc.edu.cn /ubuntu/ focal-backports main restricted universe multiverse
deb-src https: //mirrors .ustc.edu.cn /ubuntu/ focal-backports main restricted universe multiverse
deb https: //mirrors .ustc.edu.cn /ubuntu/ focal-security main restricted universe multiverse
deb-src https: //mirrors .ustc.edu.cn /ubuntu/ focal-security main restricted universe multiverse
deb https: //mirrors .ustc.edu.cn /ubuntu/ focal-proposed main restricted universe multiverse
deb-src https: //mirrors .ustc.edu.cn /ubuntu/ focal-proposed main restricted universe multiverse
---------------------------------------------------------------------------------------------
# 网易163源
deb http: //mirrors .163.com /ubuntu/ focal main restricted universe multiverse
deb http: //mirrors .163.com /ubuntu/ focal-security main restricted universe multiverse
deb http: //mirrors .163.com /ubuntu/ focal-updates main restricted universe multiverse
deb http: //mirrors .163.com /ubuntu/ focal-proposed main restricted universe multiverse
deb http: //mirrors .163.com /ubuntu/ focal-backports main restricted universe multiverse
deb-src http: //mirrors .163.com /ubuntu/ focal main restricted universe multiverse
deb-src http: //mirrors .163.com /ubuntu/ focal-security main restricted universe multiverse
deb-src http: //mirrors .163.com /ubuntu/ focal-updates main restricted universe multiverse
deb-src http: //mirrors .163.com /ubuntu/ focal-proposed main restricted universe multiverse
deb-src http: //mirrors .163.com /ubuntu/ focal-backports main restricted universe multiverse