Hello,
Each time cron starts with any task, it displays the following message to the console:

cron(pam_unix)[xxxx]: session opened for user root by (uid=0)

As I understand that's not a cron message, but pam_unix message. How can I stop them?

"pam_unix nowarn" in /etc/pam.d/common-auth and common-password does not help, the same in /etc/pam.d/common-session causes "unrecognized option" error.

Regards,
Dmitry