因为jetson系列的源都是国外的，下载中途经常断线且很慢。所以要换源，换为国内源后，下载速度更快。
而清华大学的源可以在jetson上完美使用。
所以可以更换为清华大学的源。
注意使用的是ubuntu18.04的版本。

1 备份原来的源

需要备份原来的sources.list文件

sudo cp /etc/apt/sources.list /etc/apt/sources.list.back

2 更换源

打开sourcse.list

sudo vim /etc/apt/sources.list 

删除原来sources.list内容
命令模式下输入

1000dd

按i进入编辑模式
复制下面的源到sources.list中
中科大/清华的arm64架构源

# 默认注释了源码仓库，如有需要可自行取消注释
deb [arch=armhf] https://mirrors.ustc.edu.cn/ubuntu-ports/ bionic main restricted universe multiverse
# deb-src https://mirrors.ustc.edu.cn/ubuntu-ports/ bionic main main restricted universe multiverse
deb [arch=armhf] https://mirrors.ustc.edu.cn/ubuntu-ports/ bionic-updates main restricted universe multiverse
# deb-src https://mirrors.ustc.edu.cn/ubuntu-ports/ bionic-updates main restricted universe multiverse
deb [arch=armhf] https://mirrors.ustc.edu.cn/ubuntu-ports/ bionic-backports main restricted universe multiverse
# deb-src https://mirrors.ustc.edu.cn/ubuntu-ports/ bionic-backports main restricted universe multiverse
deb [arch=armhf] https://mirrors.ustc.edu.cn/ubuntu-ports/ bionic-security main restricted universe multiverse
# deb-src https://mirrors.ustc.edu.cn/ubuntu-ports/ bionic-security main restricted universe multiverse

# 预发布软件源，不建议启用
# deb [arch=armhf] https://mirrors.ustc.edu.cn/ubuntu-ports/ bionic-proposed main restricted universe multiverse
# deb-src [arch=armhf] https://mirrors.ustc.edu.cn/ubuntu-ports/ bionic-proposed main restricted universe multiverse

保存sources.list
按esc，冒号，wq

3 update

打开终端输入

sudo apt update