aarch64架构换源失败问题解决

问题背景
在arrch64架构的Jetson TX2换源，系统是Ubuntu16.04

deb [arch=amd64,i386] http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic main restricted
deb [arch=amd64,i386] http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-updates main restricted
deb [arch=amd64,i386] http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic universe
deb [arch=amd64,i386] http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-updates universe
deb [arch=amd64,i386] http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic multiverse
deb [arch=amd64,i386] http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-updates multiverse
deb [arch=amd64,i386] http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-backports main restricted universe multiverse
deb [arch=amd64,i386] http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-security main restricted
deb [arch=amd64,i386] http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-security universe
deb [arch=amd64,i386] http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-security multiverse
deb  [arch=amd64,i386]  http://archive.ubuntu.com/ubuntu bionic universe

发现报错：

Err:1 http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports xenial-updates InRelease
  Could not connect to 192.168.1.101:7890 (192.168.1.101). - connect (111: Connection refused)
Err:2 http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports xenial-security InRelease
  Unable to connect to 192.168.1.101:7890:
Err:3 http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports xenial-backports InRelease
  Unable to connect to 192.168.1.101:7890:
Err:4 http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports xenial InRelease
  Unable to connect to 192.168.1.101:7890:
Reading package lists... Done
W: Failed to fetch http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/dists/xenial-updates/InRelease  Could not connect to 192.168.1.101:7890 (192.168.1.101). - connect (111: Connection refused)
W: Failed to fetch http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/dists/xenial-security/InRelease  Unable to connect to 192.168.1.101:7890:
W: Failed to fetch http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/dists/xenial-backports/InRelease  Unable to connect to 192.168.1.101:7890:
W: Failed to fetch http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/dists/xenial/InRelease  Unable to connect to 192.168.1.101:7890:
W: Some index files failed to download. They have been ignored, or old ones used instead.

问题所在
查阅重多教程之后发现是因为之前开了代理（但是没有成功），需要关闭一些之前的设置。
解决方法
查看 /etc/apt/apt.conf文件，如果存在类似：

Acquire::http::proxy “http://x.x.x.x:8080/”

在其前面加注释 #
查看 /etc/environment文件，如果有类似：

http_proxy=“http://x.x.x.x:8080/”

在其前面同样加注释 #
最后重新 sudo apt-get update 即可更新软件源列表