Ubuntu鏡像源配置文件所在的位置：
/etc/apt/sources.list
1. 備份已有的鏡像源
在修改鏡像源之前，最好通過UI或者命令行備份已有的鏡像源
sudo cp /etc/apt/sources.list /etc/apt/sources.list_bak
2. 查看操作系統的內核版本
lsb_release -a
如果沒有安裝lsb_release，可以通過如下命令來查看：
cat /etc/issue
3. 獲取鏡像源
根據內核版本在 sources.list文件種粘貼下方的鏡像源：（比如Ubuntu 16.04對應版本xenial）
# deb cdrom:[Ubuntu 16.04.2 LTS _Xenial Xerus_ - Release amd64 (20170215.2)]/ xenial main restricted
# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.
deb http://mirrors.aliyun.com/ubuntu/ xenial main restricted
# deb-src http://cn.archive.ubuntu.com/ubuntu/ xenial main restricted
## Major bug fix updates produced after the final release of the
## distribution.
deb http://mirrors.aliyun.com/ubuntu/ xenial-updates main restricted
# deb-src http://cn.archive.ubuntu.com/ubuntu/ xenial-updates main restricted
## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team. Also, please note that software in universe WILL NOT receive any
## review or updates from the Ubuntu security team.
deb http://mirrors.aliyun.com/ubuntu/ xenial universe
# deb-src http://cn.archive.ubuntu.com/ubuntu/ xenial universe
deb http://mirrors.aliyun.com/ubuntu/ xenial-updates universe
# deb-src http://cn.archive.ubuntu.com/ubuntu/ xenial-updates universe
## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team, and may not be under a free licence. Please satisfy yourself as to
## your rights to use the software. Also, please note that software in
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb http://mirrors.aliyun.com/ubuntu/ xenial multiverse
# deb-src http://cn.archive.ubuntu.com/ubuntu/ xenial multiverse
deb http://mirrors.aliyun.com/ubuntu/ xenial-updates multiverse
# deb-src http://cn.archive.ubuntu.com/ubuntu/ xenial-updates multiverse
## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
deb http://mirrors.aliyun.com/ubuntu/ xenial-backports main restricted universe multiverse
# deb-src http://cn.archive.ubuntu.com/ubuntu/ xenial-backports main restricted universe multiverse
## Uncomment the following two lines to add software from Canonical's
## 'partner' repository.
## This software is not part of Ubuntu, but is offered by Canonical and the
## respective vendors as a service to Ubuntu users.
# 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://security.ubuntu.com/ubuntu xenial-security main restricted
deb http://mirrors.aliyun.com/ubuntu/ xenial-security universe
# deb-src http://security.ubuntu.com/ubuntu xenial-security universe
deb http://mirrors.aliyun.com/ubuntu/ xenial-security multiverse
# deb-src http://security.ubuntu.com/ubuntu xenial-security multiverse
4. 激活新的鏡像源
sudo apt-get update
sudo apt-get upgrade