On Fri, May 05, 2017 at 10:38:42PM +0800, tumashu wrote:
> 
> isrgrootx1.pem is a package?  

isrgrootx1.pem is th eroot certificate of the Let's Encrypt certificate
authority:

https://letsencrypt.org/certs/isrgrootx1.pem.txt

Why do you ask? Is it related to BIND?