Given a CA certificate file 'foo.crt', follow these steps to install it on Ubuntu:
First, copy your CA to dir
then, update CA store
sudo cp foo.crt /usr/local/share/ca-certificates/foo.crt
That's all. You should get this output:
Updating certificates in /etc/ssl/certs... 1 added, 0 removed; done. Running hooks in /etc/ca-certificates/update.d.... Adding debian:foo.pem done. done.