I use Let’s Encrypt certificates in my Windows and Linux serves. This week I had to use the same certificate in two machines, one IIS server (Windows) and one Apache2 server (Linux Debian).
I create the certificate in Linux using certbot utility, ant it gave me four files:
I installed to Apache with no problems.
But then I tried to install the certificate to IIS 6.1 and I realized that Windows did not want that type of file. With some research on the Internet I found a solution, using the command openssl (in Linux):
openssl pkcs12 -export -out certificateforwindows.pfx -inkey privkey.pem -in cert.pem -certfile fullchain.pem
I wish this helps someone