How the UNIX Domain Socket is Used for Communications

The communication mechanism between crontab(1), at(1), atrm(1), and cron(1M) in the Trusted Solaris environment is a UNIX domain socket. See the man page for libt6(3NSL).

The cron(1M) command is modified to create and bind the UNIX domain socket at ADMIN_LOW to /etc/cron.d/CRON. The /etc/cron.d/CRON file is also used as a lock file to prevent more than one execution of the clock daemon.

After it creates the UNIX domain socket, the cron command is changed to run at ADMIN_HIGH. The /var/cron/log file is created by the clock daemon at ADMIN_HIGH. The clock daemon logs its internal messages in this log file.

An ancillary file is created in the crontabs MLD for each crontab file and in the atjobs MLD for each atjob file. Modification of a crontab or an atjob file also changes the ancillary file data. The ancillary file is named username.ad for a crontab file, and jobname.ad for an atjob file. The ancillary file contains information used by cron to set up a job.

Trusted Solaris software is delivered with the following /var/spool/cron/crontabs files:

• At the ADMIN_LOW label, pairs of crontab and ancillary files for root, uucp, adm, and sys.

• At the ADMIN_HIGH label, pairs of crontab and ancillary files for root and lp.