Where are root certificates stored in Linux?

Although root certificates exist as single files they can also be combined into a bundle. On Debian based Linux systems these root certificates are stored in the /etc/ssl/certs folder along with a file called ca-certificates. crt.

How do I know if root certificate is installed Linux?

You can perform this with the following command: sudo update-ca-certificates . You will notice that the command reports it has installed certificates if required (up-to-date installations may already have the root certificate).