Write a schedule
You edit the list with crontab -e. minute 0-59, hour 0-23, day of month 1-31, month 1-12, day of week 0-7 (0 and 7 are Sunday). A step such as */5 means "every five".
$ crontab -e # m h dom mon dow command */5 * * * * /home/me/check.sh >> /home/me/check.log 2>&1 30 3 * * 1 /home/me/backup.sh @reboot /home/me/start-bot.sh
| Schedule | Meaning |
|---|---|
*/5 * * * * | Every five minutes |
0 9 * * 1-5 | At 9:00 on weekdays |
30 3 1 * * | At 3:30 on the first day of each month |
@daily | A nickname for 0 0 * * *; @reboot runs once after startup; @daily is 0 0 * * *; @weekly is 0 0 * * 0; @monthly is 0 0 1 * * |
Three traps catch most beginners. Cron starts commands with a small environment, so write full paths. It mails or drops the output unless you redirect it to a log, as above. And when both day-of-month and day-of-week are restricted, the job runs when either matches, so 0 9 1 * 1 runs on the 1st and on every Monday.
Cron and a sleeping computer
Cron is a program inside the computer. When the computer sleeps, the program sleeps with it, so a crontab entry inside a sleeping computer does not run and cannot wake it. An entry set for 3:00 does not fire at 3:00 if the computer is asleep then.
You have three ways out. Keep the job short and let it run when the computer happens to be awake. Run a long job that keeps the computer awake while it works. Or let the platform wake the computer for you, as below.
Do you need one?
Use cron when
- Work repeats on the clock. Backups, reports, clean-up, a daily fetch.
- The timing is simple. Every N minutes, or at a fixed hour.
- You want no extra software. Cron is on most Linux servers.
Use something else when
- Work starts on an event. A payment or a message needs a webhook, not a clock.
- You need logs, retries and alerts. A systemd timer or a job runner gives more than bare cron.
Cron in Uno
Uno has scheduled tasks: a command runs on your computer on a cron schedule, and Uno keeps the history and the log of every run. In short: a scheduled task that comes due wakes a sleeping computer and runs its command; scheduled tasks are set up through the API (POST /api/v1/scheduled-tasks), so your agent can create one for you. The computer sleeps after 10 minutes with nothing to do, and a long job or an agent working overnight keeps it awake.
Small: $5 a month
What it does not do
- One exception: a scheduled task does not wake a computer whose subscription is suspended or ended.
- An ordinary crontab on a sleeping computer stays silent. For work that must start on time, use a scheduled task.
- Schedules for assistants are a separate feature: several assistants and assistant schedules are on for a few accounts so far.
Run scheduled work from $5 a month
A real Linux computer with root. It sleeps between jobs, and a scheduled task wakes it.
Small
A Telegram bot, a VPN, a small backend
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Plus
Agents that work with your laptop closed
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Pro
A product in production, a second MacBook
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Max
A team and many agents at once
$200/ month
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- 300 GB disk
- 1,024 GB cloud storage
- 5 public IPv4
Add Uno AI to any plan: 40 h of AI work a month on Small, 100 h on Plus, unlimited on Max. Today: GLM-5.3 Flash and MiMo v2.6 Pro. Or sign in with your own Claude or ChatGPT.
Questions
What is the difference between cron and a systemd timer?
Which time zone does cron use?
date to see it. Many servers use UTC, so "3:00" may not be 3:00 where you live.