On Ubuntu, SSL CA certificates are stored in subdirectories of /usr/local/share/ca-certificates. In order to add additional CA certificates, first create a new subdirectory to store your CAs:
sudo mkdir /usr/local/share/ca-certificates/added |
Then add your CA certificates to this directory. These files should have a .crt extension (e.g., my_ca.crt). Then append a line for each certificate you add to the configuration file /etc/ca-certificates.conf (e.g., “added/my_ca.crt“). Finally, run
sudo update-ca-certificates --fresh |
This command reads the file /etc/ca-certificates.conf, updates the directory /etc/ssl/certs to hold SSL certificates and generates the file /etc/ssl/certs/certificates.crt. The script update-ca-certificates will use the command c_rehash take a hash value of each .crt file. It then creates symbolic links in the directory /etc/ssl/certs for each of the files named by the hash value. This is useful as many programs require directories to be set up like this in order to find the certificates they require. /etc/ssl/certs/certificates.crt is a concatenated single-file version of CA certificates. It contains all CA certificates that were activated in /etc/ca-certificates.conf.
Use the file command to verify that the .crt files you add use Unix newline characters, otherwise the /etc/ssl/certs/certificates.crt file may not be generated properly.