Certutil

• macOS: brew install nss
• Fedora/RHEL: rpm -ivh nss-tools

certutil -N -d <database path>

Create a CSR with subject CN=<common name>,O=<realm>, for example:

• certutil -R -d <database path> -a -g <key size> -s 'CN=<common name>,O=DOMAIN.COM'

See also

• mkcert