This manual page documents briefly the update-ca-certificates command.
update-ca-certificates is a program that updates the directory /etc/ssl/certs to hold SSL certificates and generates ca-certificates.crt, a concatenated single-file list of certificates.
It reads the file /etc/ca-certificates.conf. Each line gives a pathname of a CA certificate under /usr/share/ca-certificates that should be trusted. Lines that begin with "#" are comment lines and thus ignored. Lines that begin with "!" are deselected, causing the deactivation of the CA certificate in question. Certificates must have a .crt extension in order to be included by update-ca-certificates.
Furthermore all certificates with a .crt extension found below /usr/local/share/ca-certificates are also included as implicitly trusted.
Before terminating, update-ca-certificates invokes run-parts on /etc/ca-certificates/update.d and calls each hook with a list of certificates: those added are prefixed with a +, those removed are prefixed with a -.