cdituri/feature/qemu leverage qcow2 disk format

cdituri commented 4 years ago

Greetings nix-community/nixbox maintainers, thank you for your efforts!

This pull request does two things:

Introduces disk_size and memory packer (build-time) variables, and their defaults. Usage example:
```
packer build -var 'disk_size=40960' -var 'memory=4096' -only qemu nixos-x86_64.json
```
Switches the qemu/libvirt builder to leverage qcow2 for better efficiency and thinly provisioned disks. As a result, we skip disk zero-out in the postinstall.sh when $PACKER_BUILDER_TYPE is qemu, since the backing image is sparse to begin with.

Resultant qemu/libvrit qcow2 backed vagrant .box for the packer "usage example" above:

$ du -h nixos-19.09-libvirt-x86_64.box 
3.2G    nixos-19.09-libvirt-x86_64.box

zimbatm commented 4 years ago

thanks!

cdituri commented 4 years ago

no prob @zimbatm, happy to help.

nix-community / nixbox