Access to the AFS system works based on a system of authentication tokens, obtained from the Kerberos tickets system. This system is transparent to most users of the sigma cluster (tokens and tickets are automatically obtained when logging in).
However, it must be borne in mind that, for security reasons, AFS tokens have a limited duration in time. If the ticket is not renewed within this period, a failure in disk access may be noted. In these cases, it is necessary to use the command “kinit” and “aklog” in sequence to renew the ticket.