How to change the schedule of a Kubernetes cronjob or how to start it manually?
Is there a simple way to change the schedule of a kubernetes cronjob like kubectl change cronjob my-cronjob "10 10 * * *"? Or any other way without needing to do kubectl apply -f deployment.yml? The latter can be extremely cumbersome in a complex CI/CD setting because manually editing the deployment yaml is often not desired, especially not if the file is created from a template in the build process.
Alternatively, is there a way to start a cronjob manually? For instance, a job is scheduled to start in 22 hours, but I want to trigger it manually once now without changing the cron schedule for good (for testing or an initial run)?
Answer
You can update only the selected field of resourse by patching it
patch -h
Update field(s) of a resource using strategic merge patch, a JSON merge patch, or a JSON patch.
JSON and YAML formats are accepted.
Please refer to the models in
https://htmlpreview.github.io/?https://github.com/kubernetes/kubernetes/blob/HEAD/docs/api-reference/v1/definitions.html
to find if a field is mutable.
As provided in comment for ref :
kubectl patch cronjob my-cronjob -p '{"spec":{"schedule": "42 11 * * *"}}'
Also, in current kubectl versions, to launch a onetime execution of a declared cronjob, you can manualy create a job that adheres to the cronjob spec with
kubectl create job --from=cronjob/mycron