at command in Linux: a one-time scheduled job, examples

Q: The command "was not found" inside at

Like cron, at has a minimal environment (though at does save the current env at the time the job is queued — at -c ID shows it). Absolute paths are still more reliable (see env-vars).

Q: I need to cancel it

atq (find the id) → atrm <id>.

Q: at: command not found / no atd

The at package isn't installed or the daemon isn't running: sudo apt install at, sudo systemctl enable --now atd.

Q: One-off vs. recurring vs. a service

One-off — at; on a schedule — cron/systemd timers; a permanent service — a systemd unit. "When the machine is idle" — batch.

Overview

at runs a command once at a given time (unlike cron's repeating schedule). Handy for one-off deferred actions: reboot at night, shut down in an hour, auto-revert a firewall rule. The daemon is atd.

bash

systemctl status atd
echo "systemctl restart nginx" | at 03:00      # run at 3:00

Options

6

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Below are the main flags of at, atq, atrm; the full list is in man at.

Option	What it does	Example
`-f` file	Read commands from a script file instead of stdin.	`at -f script.sh 02:00`
`-l`	List the current user's queued jobs (same as atq).	`at -l`
`-c` job_id	Show the contents and environment of a queued job.	`at -c 5`
`-m`	Send mail to the user even if the command produced no output.	`at -m 03:00`
`-r` job_id	Remove a job from the queue (same as atrm). dangerous	`at -r 5`
`-q` queue	Put the job in a different queue (affects the nice priority it runs with).	`at -q b 03:00`

Nothing found. Try a shorter query.

Recipes

2

Commands

bash

at 03:00                          # interactive (type commands, Ctrl+D to end)
at now + 1 hour                   # in an hour (minutes/hours/days/weeks)
at 14:30 tomorrow
at 2026-07-01                     # on a date
at -f script.sh 02:00             # run a script file
echo "cmd" | at midnight          # from a pipe
batch                             # run once the load drops (load < 1.5)

atq                               # job queue (id, time, queue)
at -c 5                           # show the contents (and environment) of job #5
atrm 5                            # remove a job (same as at -r 5)

Time formats

at 17:00              at 5pm              at now + 30 minutes
at midnight           at noon             at teatime   (16:00)
at 10:00 Jul 31       at 10am tomorrow    at now + 2 days

Access is controlled by /etc/at.allow / /etc/at.deny (who can queue jobs).

Troubleshooting

5

The job did not run

The atd daemon must be running (systemctl status atd). at's result is sent by mail to the local user (/var/mail/); stdout/stderr go there, not to a screen. Redirect it yourself: echo "cmd > /tmp/out 2>&1" | at ....

The command "was not found" inside at

Like cron, at has a minimal environment (though at does save the current env at the time the job is queued — at -c ID shows it). Absolute paths are still more reliable (see env-vars).

I need to cancel it

atq (find the id) → atrm <id>.

at: command not found / no atd

The at package isn't installed or the daemon isn't running: sudo apt install at, sudo systemctl enable --now atd.

One-off vs. recurring vs. a service

One-off — at; on a schedule — cron/systemd timers; a permanent service — a systemd unit. "When the machine is idle" — batch.

at — a one-time scheduled job

Cheat sheet