Cron jobs are not supported on Sherlock, and going forward they won't be allowed anymore.

Due to various past incidents, we had to disable the functionality, to prevent runaway cron jobs to take out entire login nodes. Moreover, compute and login nodes could be redeployed at any time, meaning that cron jobs scheduled there could go away without the user being notified, and cause all sorts of unexpected results.

To replace the functionality that cron jobs provide, we recommend an alternative solution using regularly scheduled jobs, for users and groups which need to run specific tasks at regular intervals. Please see our Recurring jobs documentation for more details.