Installing a self-signed certifcate as a trusted root CA in Debian

Firstly copy your certifcate to /usr/share/ca-certifcates:

cp /path/to/certificate.pem /usr/share/ca-certificates

and then ensure the ca-certifcates package is installed with:

apt-get install ca-certificates

and finally install the certifcate with:

dpkg-reconfigure ca-certificates

Select 'Yes' at the dialog prompt and ensure that your certifcate is checked.