问题比较紧急，有空回来详细补一下。
$ sudo apt update Err:7 https://mirrors.tuna.tsinghua.edu.cn/gitlab-ce/ubuntu bionic/main Sources Certificate verification failed: The certificate is NOT trusted. The certificate chain uses expired certificate. Could not handshake: Error in the certificate verification. [IP: 101.6.15.130 443]点击复制复制失败已复制
方法一
$ sudo apt install ca-certificates点击复制复制失败已复制
方法二
deb [trusted=yes] http://ppa.launchpad.net/repo_name/pkg/ubuntu vivid main deb-src [trusted=yes] http://ppa.launchpad.net/repo_name/pkg/ubuntu vivid
