问题

Err:2 http://cn.archive.ubuntu.com/ubuntu focal/universe amd64 libflann-dev amd64 1.9.1+dfsg-9build1
Connection failed [IP: 91.189.91.38 80]
E: Failed to fetch http://cn.archive.ubuntu.com/ubuntu/pool/universe/f/flann/libflann1.9_1.9.1+dfsg-9build1_amd64.deb Connection failed [IP: 91.189.91.38 80]
E: Failed to fetch http://cn.archive.ubuntu.com/ubuntu/pool/universe/f/flann/libflann-dev_1.9.1+dfsg-9build1_amd64.deb Connection failed [IP: 91.189.91.38 80]

 

解决方法

https://mirror.tuna.tsinghua.edu.cn/help/ubuntu/
sudo vi /etc/apt/sources.list
sudo apt-get update
sudo apt-get install libflann1.9

参考

1. 

​​https://mirror.tuna.tsinghua.edu.cn/help/ubuntu/​​