CronJobs and Schedule Syntax

A CronJob creates a Job from its jobTemplate on a cron schedule of minute, hour, day of month, month and weekday: 30 2 * * * is 02:30 daily, */15 9-17 * * 1-5 every quarter hour in weekday office hours. timeZone (stable since 1.27) takes an IANA name. Database Backups's backup, run every minute to watch it:

A backup CronJob observed over two runs, then deletedShell

kubectl apply -f - >/dev/null <<'EOF'
apiVersion: batch/v1
kind: CronJob
metadata: { name: db-backup }
spec:
  schedule: "* * * * *"          # nightly in real life: "30 2 * * *"
  timeZone: Asia/Kuala_Lumpur
  concurrencyPolicy: Forbid
  successfulJobsHistoryLimit: 2
  jobTemplate:
    spec:
      template:
        spec:
          restartPolicy: Never
          containers:
          - name: dump
            image: localhost:33500/postgres:18
            command: [sh, -c, 'echo "$(date +%T) dump: $(pg_dump | gzip | wc -c) bytes"']
            envFrom: [{ configMapRef: { name: api-config } }]
            env:
            - name: PGUSER
              valueFrom: { secretKeyRef: { name: db-credentials, key: username } }
            - name: PGPASSWORD
              valueFrom: { secretKeyRef: { name: db-credentials, key: password } }
EOF
until [ "$(kubectl get jobs -o name | grep -c db-backup)" -ge 2 ]; do sleep 5; done
kubectl wait --for=condition=Complete $(kubectl get jobs -o name | grep db-backup) >/dev/null
kubectl get jobs | grep -E '^NAME|db-backup'
for j in $(kubectl get jobs -o name | grep db-backup); do kubectl logs $j; done
kubectl delete cronjob db-backup && sleep 5 && kubectl get jobs -o name | grep -c db-backup

Output

NAME                 STATUS     COMPLETIONS   DURATION   AGE
db-backup-29839238   Complete   1/1           4s         65s
db-backup-29839239   Complete   1/1           4s         5s
16:38:01 dump: 1239 bytes
16:39:02 dump: 1238 bytes
cronjob.batch "db-backup" deleted from booknest namespace
0

Job names end in the scheduled minute since the Unix epoch, and deleting the CronJob deleted its Jobs. concurrencyPolicy handles a run still going at the next tick: Allow (default) overlaps, Forbid skips, Replace cancels the old run. A missed tick still runs within startingDeadlineSeconds. A real backup would copy the dump to object storage rather than count its bytes.

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