CA Certificate under Debian

Add your custom CA Certificate in the folder

/usr/local/share/ca-certificates/<yoursubfolder>/<yourcertificate.crt>

Use the command update with -f option to add missing symlink

sudo update-ca-certificates -f

In return, the command will show you the added certificates.

You can verify the result in folder /etc/ssl/certs/.

Keep in mind to use this command because /etc/ssl/certs/ca-certificates.crt will be concatenated with all certificates in same time

Source

https://quennec.fr/trucs-astuces/systèmes/gnulinux/utilisation/installer-les-certificats-racine-cacert-sur-debianubuntu
https://www.cyberciti.biz/faq/update-ca-certificates-command-examples-in-linux-to-ssl-ca-certificates/