1. 首先我們要找到國內的映象源路徑

我選擇了清華的映象源，連結如下：
https://mirrors.tuna.tsinghua.edu.cn/help/ubuntu/
開啟連結如下圖：

接下來按圖中提示操作即可，當然也可以自己搜尋其他的映象源。

2. 備份系統自帶更新源配置檔案

開啟終端切換到管理員（修改配置檔案需要較高許可權，如不切換也可以在每條命令前加sudo，不過個人感覺有點麻煩），進入 /etc/apt 目錄，找到 sources.list 檔案，進行備份，如下圖：

也可以直接用命令：cp  /etc/apt/source.list  /etc/apt/source.list.backup

3.修改配置檔案source.list內容

輸入命令：gedit source.list 開啟檔案，把檔案內容全部刪除，再把更新源路徑貼上進來。

粘貼後如下圖：

之後儲存，並退出。

4. 更新源

輸入命令：sudo apt-get update

開始更新源

更新完成 ：

 

至此，更新源就已經成功了！

如果使用此軟體源有部分問題，推薦使用“推薦軟體源.txt”中的軟體源，將程式碼直接貼上到剛剛開啟的source.list檔案頭部就行了。

推薦軟體源1（阿里雲）：

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

推薦軟體源2：

deb http://mirrors.aliyun.com/ubuntu/ quantal main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ quantal-security main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ quantal-updates main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ quantal-proposed main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ quantal-backports main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ quantal main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ quantal-security main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ quantal-updates main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ quantal-proposed main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ quantal-backports main restricted universe multiverse
# 預設註釋了原始碼映象以提高 apt update 速度，如有需要可自行取消註釋
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-updates main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-updates main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-backports main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-backports main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-security main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-security main restricted universe multiverse

OK，這樣的話，就可以比較流暢的使用ubuntu系統了！