atd

Start the at daemon

$ atd

$ atd -f

$ atd -d

$ atd -b [120]

$ atd -s

atd [-d] [-f] [-s] [-l loadavg] [**-b** interval_]

atd is the daemon that executes jobs scheduled with the at command. It runs in the background, periodically checking /var/spool/at/ for pending jobs and executing them at their scheduled times.
Jobs are submitted using at for time-specific scheduling or batch for load-based execution. The daemon runs jobs on behalf of the user who scheduled them, inheriting their environment and permissions.
Access control is managed through /etc/at.allow and /etc/at.deny. If at.allow exists, only listed users can schedule jobs. If only at.deny exists, all users except those listed can schedule jobs. If neither exists, only root can use at.
Related commands:
- at - schedule a job for a specific time
- atq - list pending jobs
- atrm - remove a pending job
- batch - schedule a job for when system load permits

-d

Debug mode; print errors to stderr instead of syslog (implies -f)

Run in foreground instead of daemonizing

Process the at/batch queue once and exit

Limit batch job execution to when system load is below this value (default: 1.5)

Minimum seconds between starting batch jobs (default: 60)

The atd spool directory (/var/spool/at/) does not work correctly when mounted via NFS, even with norootsquash. Jobs inherit the environment from when they were scheduled, not the current environment. The daemon must be running for scheduled jobs to execute.

The at command and its daemon have origins in early Unix systems, dating back to Version 7 Unix in 1979. The concept of deferred command execution was part of the original Unix job control philosophy. The modern implementation includes the batch command for load-sensitive scheduling, making it useful for resource-intensive tasks that should run during low-usage periods.

at(1), atq(1), atrm(1), batch(1), cron(8), crontab(1)