VMWare images are huge

[nesies]

On VMWare, the template/OVF images are X0GB even if the OS takes only several GB.

If the feature exists on packer, it would be great to use it.

(if i export an OVA and then import it, the result is a less than 3GB virtual machine)

[tenthirtyam]

Do you have thin provisioned set?

[nesies]

yes thin is set.
During the installation, the RPMs are downloaded and then deleted, which seems is not reclaimed
(datastore on NFS)

[tenthirtyam]

NFS is thin-provisioned by nature, and the VMDKs will grow as needed based on usage up to the capacity defined for the virtual disks. You could add a step using dd to zero-fill the unused space, but the template size will remain the same as the max size consumed during the build.

You could also add the use of the vsphere-template post-processor to save it as a new template wish would reduce the size of the final
image since it would save a new template and can then delete the build source if you like.