Install a CA on debian systems

Installing a CA Certificate

Given a CA certificate file foo.crt, follow these steps to install it on Ubuntu:

1. first method : Create a directory for extra CA certificates in /usr/share/ca-certificates:

sudo mkdir /usr/share/ca-certificates/extra

Copy the CA .crt file to this directory:

sudo cp foo.crt /usr/share/ca-certificates/extra/foo.crt

Let Ubuntu add the .crt file's path relative to /usr/share/ca-certificates to /etc/ca-certificates.conf:

sudo dpkg-reconfigure ca-certificates

2. second method - without user interaction (which I use for docker): copy the certificate in /usr/local/share/

execute update-ca-certificates :

Updating certificates in /etc/ssl/certs...
1 added, 0 removed; done.
Running hooks in /etc/ca-certificates/update.d...
done.