Flag '-c' in kubernetes cronjobs command/args

Question

What does the flag '-c' do in the Kubernetes Cronjob?

kind: CronJob
metadata:
  name: hello
spec:
  schedule: "* * * * *"
  jobTemplate:
    spec:
      template:
        spec:
          containers:
          - name: hello
            image: busybox
            imagePullPolicy: IfNotPresent
            command:
            - /bin/sh
            - -c
            - date; echo Hello from the Kubernetes cluster
          restartPolicy: OnFailure

Hello, it is a standard shell. The "-c" stands for command. So it asks to the shell binary to run the date command and then echo a string. You can maybe get a better understanding if you run "/bin/sh --help" in any linux container. — François, Jan 19 '22 at 12:51

score 1 · Answer 1 · answered Feb 18 '22 at 11:43

Community wiki for clearness and further searches.

@François is completely correct. /bin/sh -c comes directly from unix and simply means command you issue after shell. This is NOT a parameter for k8s cronjob :

If the -c option is present, then commands are read from string. If there are arguments after the string, they are assigned to the positional parameters, starting with $0.

You can also check What is /bin/sh -c?

score 0 · Answer 2 · answered Jan 19 '22 at 12:50

0

The "-c" flag does not belong to the Cronjob, it is used by unix sh executing the command:

/bin/sh -c date; echo Hello from the Kubernetes cluster

So you need to read the documentation for unix sh, not kubernetes.

answered Jan 19 '22 at 12:50

KubePony

144
1
7

I never said that it has to do something with Kubernetes. I just encountered it in Cronjob doc. My question was: what does it do. @Francois response was rather helpful. Thanks for your answer anyway – panos Jan 19 '22 at 13:48

Flag '-c' in kubernetes cronjobs command/args

2 Answers2