Here is a JSON file to be used with Packer on a Mac. It will create a local VM for Fusion. The variables section is ‘use it or loose it’. I use it in order to pass variables from the CLI when creating several VMs.

The variables are passed to the Linux Boot Menu i.e. by pressing [TAB]. The builders -> boot_command is where the variables are inserted as seen in the JSON files boot_command section.

{
  "variables": {
    "hostname": "rhdev100",
    "domain": "rocksolid.com",
    "ip": "192.168.198.30",
    "gateway": "192.168.198.2",
    "netmask": "255.255.255.0",
    "dns1": "192.168.198.2",
    "dns2": "192.168.198.3"
  	},
  "builders": [
    {
      "boot_command": [
	"<tab>",
	"vmlinuz initrd=initrd.img ",
	"myhostname={{user `hostname`}} ",
	"mydomain={{user `domain`}} ",
	"myip={{user `ip`}} ",
	"mygateway={{user `gateway`}} ",
	"mynetmask={{user `netmask`}} ",
	"mydns1={{user `dns1`}} ",
	"mydns2={{user `dns2`}} ",
	"ks=http://192.168.198.1:8000/Build/kickstart/rh.cfg <enter><wait>"
      ],
      "boot_wait": "10s",
      "disk_size": 40000,
      "guest_os_type": "centos-64",
      "headless": false,
      "iso_checksum": "32c7695b97f7dcd1f59a77a71f64f2957dddf738",
      "iso_checksum_type": "sha1",
      "iso_url": "http://192.168.198.1:8000/packer/ISO/CentOS-6.5-x86_64-bin-DVD1.iso",
      "output_directory": "/Users/TheDude/VirtualMachines/{{user `hostname`}}",
      "shutdown_command": "shutdown -h now",
      "ssh_password": "SecretPasswd",
      "ssh_port": 22,
      "ssh_username": "root",
      "ssh_wait_timeout": "360s",
      "tools_upload_path": "/var/tmp/linux.iso",
      "tools_upload_flavor": "linux",
      "type": "vmware-iso",
      "vm_name": "{{user `fqdn`}}",
      "vmx_data": {
        "ethernet0.present": "TRUE",
	"ethernet0.virtualDev": "vmxnet3",
        "memsize": "512",
        "numvcpus": "1",
        "cpuid.coresPerSocket": "1",
        "scsi0:0.fileName": "disk.vmdk",
        "scsi0:0.present": "TRUE",
        "scsi0:0.redo": ""
      }
    }
  ],
    "provisioners": [
    {
      "execute_command": "echo 'TheDude' | {{.Vars}} sudo -S -E bash '{{.Path}}'",
      "scripts": [
        "scripts/yum.sh",
        "scripts/sysctl.sh",
        "scripts/network.sh",
	"scripts/vmtoolslocal.sh"
      ],
      "type": "shell"
    }
   ]
}