【ERROR】cannot verify xxx certificate, issued by ‘/C=US/O=Let’s Encrypt/CN=R3’:use `--no-check-certif

当我们使用wget下载不安全的的东西是会提示下列内容

ERROR: cannot verify lug.ustc.edu.cn's certificate, issued by ‘/C=US/O=Let's Encrypt/CN=R3’:
  Issued certificate has expired.
To connect to lug.ustc.edu.cn insecurely, use `--no-check-certificate'.

解决方法

sudo yum install -y ca-certificates

但是运行上述代码时，可能会出现下面问题

 Run "yum repolist all" to see the repos you have.
 To enable Red Hat Subscription Management repositories:
     subscription-manager repos --enable <repo>
 To enable custom repositories:
     yum-config-manager --enable <repo>

这是可以通过更换yum源来解决问题

wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo