我对 Ubuntu 很陌生。我也支持安全代理。当我尝试运行时sudo apt-get update，出现以下错误。
blah@blah-hp-15-notebook-pc:~$ sudo apt-get update
Err http://security.ubuntu.com vivid-security InRelease
Err http://in.archive.ubuntu.com vivid InRelease
Err http://security.ubuntu.com vivid-security Release.gpg
Cannot initiate the connection to security.ubuntu.com:80 (2001:67c:1360:8c01::18). - connect (101: Network is unreachable) [IP: 2001:67c:1360:8c01::18 80]
Err http://in.archive.ubuntu.com vivid-updates InRelease
Err http://in.archive.ubuntu.com vivid-backports InRelease
Err http://in.archive.ubuntu.com vivid Release.gpg
Cannot initiate the connection to in.archive.ubuntu.com:80 (2001:67c:1360:8c01::18). - connect (101: Network is unreachable) [IP: 2001:67c:1360:8c01::18 80]
Err http://in.archive.ubuntu.com vivid-updates Release.gpg
Cannot initiate the connection to in.archive.ubuntu.com:80 (2001:67c:1360:8c01::18). - connect …apt ×1