During some installation of the VirtualMin panel you may encounter the error:
Connecting to software.virtualmin.com (software.virtualmin.com)|126.96.36.199|:443... connected.
ERROR: cannot verify software.virtualmin.com's certificate, issued by '/C=US/O=Let\'s Encrypt/CN=R3': Issued certificate has expired.
Throughout this guide, we will roll a simple fix which would allow you to bypass the error.
The error may occur upon downloading the installation file with the command:
In which case you may add the -no-check-certificate flag to wget:
wget --no-check-certificate https://software.virtualmin.com/gpl/scripts/install.sh
However, upon running the install.sh you may encounter the same error. In which case you would need to reinstall the package ca-certificates of your server.
To proceed on CentOS you would need to run the command:
yum -y reinstall ca-certificates
On Debian / Ubuntu
apt-get --reinstall install ca-certificates
That's it. You may run the installation command again and it should be working flawlessly.