Cromwell assumes that bash is available and uses it to execute the wrapper `script` to housekeep files and globs before and after the execution of the actual command. However, some docker images (for example, `alpine`) has a different shell by default and only provide bash after explicit installation. It seems that the `script` comprises rudimentary commands and pipes and a full-fledged `bash` is not really needed. Check whether the simple `/bin/sh` can be used instead.