Run a cron job every 30 seconds

Q: How do I run a job every 30 seconds with a systemd timer?

OnCalendar=*-*-* *:*:00/30 UTC . systemd timer uses OnCalendar=, not cron lines.

*/30 * * * * * Check it below, then take the line for any of 17 schedulers.

Click to edit · paste a crontab line · hover a field for its values

Every 30 seconds.

Nothing to watch out for on Spring @Scheduled.

Annotation

@Scheduled(cron = "*/30 * * * * *", zone = "UTC")
public void job() { ... }

Details

Upcoming runs

Calendar Every day

Between two dates

Daylight saving

When things go wrong Server off: Skipped

Server was off: Skipped. Schedules live in memory.
Last run still going: Never overlaps. The next run is timed from when the last one ended, so slots that pass are skipped.
A run fails: Logged and suppressed. Later runs still happen.
Time zone: The scheduler's zone, or zone = on the annotation.
Precision: 1 second.

Sources: github.com,docs.spring.io

Other schedulers As written in 4 of 16

✗ Debian / Ubuntu cron Debian / Ubuntu cron takes 5 fields: minute hour day month weekday. Debian / Ubuntu cron can't run this: it has no seconds field; a minute is the smallest step. vs RunWisp
✗ cronie cronie takes 5 fields: minute hour day month weekday. cronie can't run this: it has no seconds field; a minute is the smallest step. vs RunWisp
✗ BusyBox crond BusyBox crond takes 5 fields: minute hour day month weekday. BusyBox crond can't run this: it has no seconds field; a minute is the smallest step.
↻ systemd timer *-*-* *:*:00/30 UTC systemd timer uses OnCalendar=, not cron lines. vs RunWisp
✓ RunWisp */30 * * * * *
✗ Kubernetes CronJob Kubernetes CronJob takes 5 fields: minute hour day month weekday. Kubernetes CronJob can't run this: it has no seconds field; a minute is the smallest step.
✓ Ofelia */30 * * * * * vs RunWisp
✗ Dagu Dagu takes 5 fields: minute hour day month weekday. Dagu can't run this: it has no seconds field; a minute is the smallest step. vs RunWisp
✓ PM2 cron_restart */30 * * * * * vs RunWisp
✓ Jobber */30 * * * * * vs RunWisp
✗ GitHub Actions GitHub Actions takes 5 fields: minute hour day month weekday. GitHub Actions can't run this: it has no seconds field; a minute is the smallest step.
✗ GitLab CI schedule GitLab CI schedule takes 5 fields: minute hour day month weekday. GitLab CI schedule can't run this: it has no seconds field; a minute is the smallest step.
✗ AWS EventBridge Scheduler AWS cron() needs a ? in either day-of-month or day-of-week. AWS EventBridge Scheduler can't run this: it has no seconds field; a minute is the smallest step.
✗ Google Cloud Scheduler Google Cloud Scheduler takes 5 fields: minute hour day month weekday. Google Cloud Scheduler can't run this: it has no seconds field; a minute is the smallest step.
✗ Jenkins Jenkins takes 5 fields: minute hour day month weekday. Jenkins can't run this: it has no seconds field; a minute is the smallest step.
↻ Quartz */30 * * * * ? Quartz needs a ? in either day-of-month or day-of-week.

✓ works as written · ↻ different syntax · ≠ runs at other times · ? not documented · ✗ can't

Schedulers

Every 30 seconds, in every scheduler

Works as written in 5 of 17. Times are UTC; the checker above takes any zone.

Runs in 2027: 1,051,200
Days with a run: 365
Longest gap: 30 s

Plain cron can't go below a minute. The usual crontab workaround is two lines, * * * * * cmd and * * * * * sleep 30; cmd, and the second run drifts if the first is slow.

Scheduler		Line	Notes
Debian / Ubuntu cron	✗		Debian / Ubuntu cron takes 5 fields: minute hour day month weekday. Debian / Ubuntu cron can't run this: it has no seconds field; a minute is the smallest step.
cronie	✗		cronie takes 5 fields: minute hour day month weekday. cronie can't run this: it has no seconds field; a minute is the smallest step.
BusyBox crond	✗		BusyBox crond takes 5 fields: minute hour day month weekday. BusyBox crond can't run this: it has no seconds field; a minute is the smallest step.
systemd timer	↻	`OnCalendar=--* ::00/30 UTC`	systemd timer uses OnCalendar=, not cron lines.
RunWisp	✓	`/30 * * * *`	Works as written.
Kubernetes CronJob	✗		Kubernetes CronJob takes 5 fields: minute hour day month weekday. Kubernetes CronJob can't run this: it has no seconds field; a minute is the smallest step.
Ofelia	✓	`/30 * * * *`	Works as written.
Dagu	✗		Dagu takes 5 fields: minute hour day month weekday. Dagu can't run this: it has no seconds field; a minute is the smallest step.
PM2 cron_restart	✓	`/30 * * * *`	Works as written.
Jobber	✓	`/30 * * * *`	Works as written.
GitHub Actions	✗		GitHub Actions takes 5 fields: minute hour day month weekday. GitHub Actions can't run this: it has no seconds field; a minute is the smallest step.
GitLab CI schedule	✗		GitLab CI schedule takes 5 fields: minute hour day month weekday. GitLab CI schedule can't run this: it has no seconds field; a minute is the smallest step.
AWS EventBridge Scheduler	✗		AWS cron() needs a ? in either day-of-month or day-of-week. AWS EventBridge Scheduler can't run this: it has no seconds field; a minute is the smallest step.
Google Cloud Scheduler	✗		Google Cloud Scheduler takes 5 fields: minute hour day month weekday. Google Cloud Scheduler can't run this: it has no seconds field; a minute is the smallest step.
Jenkins	✗		Jenkins takes 5 fields: minute hour day month weekday. Jenkins can't run this: it has no seconds field; a minute is the smallest step.
Quartz	↻	`/30 * * * ?`	Quartz needs a ? in either day-of-month or day-of-week.
Spring @Scheduled	✓	`/30 * * * *`	Works as written.

✓ works as written · ↻ different syntax · ≠ runs at other times · ? not documented · ✗ can't

RunWisp

Cron runs the line. Nobody tells you how it went.

RunWisp is an open-source cron replacement that ships as a single binary. It reads the same cron line and keeps a record of every run: output, exit code, duration.

crontab

# Debian / Ubuntu cron takes 5 fields: minute hour day month weekday. Debian / Ubuntu cron can't run this: it has no seconds field; a minute is the smallest step.

runwisp.toml

[tasks.job]
cron     = "*/30 * * * * *"
timezone = "UTC"
run      = '/usr/local/bin/job.sh'

	cron	RunWisp
The server was off at run time	Skipped. anacron only catches up cron.daily, weekly and monthly.	Runs the most recent missed run at start-up (catch_up = 1) and sends a missed-run alert.
The last run is still going	Starts another copy on top.	Queues it. on_overlap = "queue" is the default.
A run fails	Output is mailed if MAILTO and a mail server work. No output, no mail, whatever the exit code.	Marked failed and sent to your alert channels. retry_attempts adds retries.

Keep your crontab. sudo runwisp takeover runs it where it is and retires cron, crontab -e keeps working, and runwisp service uninstall puts cron back. It needs Linux with systemd; elsewhere, runwisp import cron converts the file. RunWisp doesn't do L, W or #, and it runs on one machine, not a cluster. Moving from cron →

FAQ

Questions

What does */30 * * * * * mean?

Every 30 seconds. In 2027 that's 1,051,200 runs on 365 days. Times are in the scheduler's time zone, usually the server's.

How do I run a job every 30 seconds in a crontab?

Debian / Ubuntu cron takes 5 fields: minute hour day month weekday. Debian / Ubuntu cron can't run this: it has no seconds field; a minute is the smallest step.

How do I run a job every 30 seconds with a systemd timer?

OnCalendar=*-*-* *:*:00/30 UTC. systemd timer uses OnCalendar=, not cron lines.

How do I run a job every 30 seconds in a Kubernetes CronJob?

Kubernetes CronJob takes 5 fields: minute hour day month weekday. Kubernetes CronJob can't run this: it has no seconds field; a minute is the smallest step.

How do I run a job every 30 seconds in GitHub Actions?

GitHub Actions takes 5 fields: minute hour day month weekday. GitHub Actions can't run this: it has no seconds field; a minute is the smallest step.

How do I run a job every 30 seconds on AWS EventBridge?

AWS cron() needs a ? in either day-of-month or day-of-week. AWS EventBridge Scheduler can't run this: it has no seconds field; a minute is the smallest step.

Similar schedules

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