1、 Could not connect to security.ubuntu.com:80 (91.189.91.93), connection timed out
Reading package lists… Done
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/bionic-security/InRelease Could not connect to security.ubuntu.com:80 (91.189.91.93), connection timed out
W: Some index files failed to download. They have been ignored, or old ones used instead.
sudo apt-get update && apt-get upgrade