Adding a certificate to the system store
Debian
Fortunately it is straightforward, since you can tell Ubuntu/Debian to update its root certificate list to include any certificates stored in the /usr/local/share/ca-certificates directory.
- upload the certificate to /usr/local/share/ca-certificates
- anything with a .crt extension is automatically trusted
- if desired, you can create subdirectories to organize certificates
- update the certificate bundle
sudo update-ca-certificates