I found out that if you enter the vagrant machine, for example quick-dev, and go to the /tmp/ directory, the Metron system has created a lot of .jar files in this folder. If you delete .jar files, it does not affect the functionality of the Metron system, and you will get back a lot of used disk-space. I got back huge amount of disk-space after deleting these files. After I left the system running, I saw that the Metron system is again producing these jar files slowly in the /tmp/ folder.
It would be good if someone can explain what these .jar files are, and how the system uses these .jar files.