Ubuntu — Schedule One-Time Commands with `at`

cron handles recurring tasks. at handles one-time execution — run a command or script once at a specific future time. Useful for a planned reboot, a delayed script run, or anything you need scheduled exactly once.

Pre-requisites

Ubuntu 22.04+ (or any Debian-based system)
sudo access

Install

sudo apt install at -y

Start and enable the atd daemon:

sudo systemctl enable --now atd

Verify:

sudo systemctl status atd

Schedule a Job

at <time>

at opens an interactive prompt. Enter the command, then press Ctrl+D to save:

at now + 10 hours
warning: commands will be executed using /bin/sh
at> reboot
at> <EOT>
job 1 at Mon May 26 08:00:00 2026

Commands requiring sudo

Prefix the command with sudo inside the at prompt as normal — the job runs under the current user's permissions.

Time formats

now + 10 minutes
now + 2 hours
now + 3 days
now + 1 week
tomorrow
5:00 AM tomorrow
10:00 PM
15:30
10:00 AM next week
next friday
01/26/2026 08:00

Read Commands from a File

at now + 2 hours < commands.txt

Each line in commands.txt is a separate command, executed in sequence.

List Scheduled Jobs

atq

at -l is an alias for the same command.

Output shows job number, scheduled time, queue, and owner:

1   Mon May 26 08:00:00 2026 a user

Inspect a Job

at -c <job_number>

Shows the full environment and commands that will be executed.

Remove a Job

atrm <job_number>

Remove all pending jobs:

for i in $(atq | awk '{print $1}'); do atrm $i; done

Common Issues

Symptom	Cause	Fix
`bash: at: command not found`	Package not installed	`sudo apt install at`
Job does not run	`atd` not running	`sudo systemctl start atd`
Job runs but produces no output	Output goes to local mail by default	Redirect output: `mycommand > /tmp/out.log 2>&1`

Ubuntu — Schedule One-Time Commands with at