This directory /usr/share/pki/ca-trust-source/ contains CA certificates and trust settings in the PEM file format. The trust settings found here will be interpreted with a low priority - lower than the ones found in /etc/pki/ca-trust/source/ . ============================================================================= QUICK HELP: To add a certificate in the simple PEM or DER file formats to the list of CAs trusted on the system: Copy it to the /usr/share/pki/ca-trust-source/anchors/ subdirectory, and run the update-ca-trust command. If your certificate is in the extended BEGIN TRUSTED file format, then place it into the main source/ directory instead. ============================================================================= Please refer to the update-ca-trust(8) manual page for additional information.