Flag '-c' in kubernetes cronjobs command/args
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@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?