QEMU Headless

packer.json

{
  "builders":
  [
    {
      "type": "qemu",
      "iso_url": "http://releases.ubuntu.com/14.04.1/ubuntu-14.04.1-server-amd64.iso",
      "iso_checksum": "ca2531b8cd79ea5b778ede3a524779b9",
      "iso_checksum_type": "md5",
      "output_directory": "out",
      "shutdown_command": "sudo shutdown -P now",
      "disk_size": 100000,
      "format": "qcow2",
      "headless": true,
      "accelerator": "kvm",
      "http_directory": "http",
      "ssh_username": "packer",
      "ssh_password": "packer",
      "ssh_port": 22,
      "ssh_wait_timeout": "1h",
      "vm_name": "packer",
      "net_device": "virtio-net",
      "disk_interface": "virtio",
      "boot_wait": "5s",
      "qemuargs": [
        ["-m", "1024M"]
      ],
      "boot_command": [
        "<esc>",
        "<esc>",
        "<enter>",
        "<wait>",
        "/install/vmlinuz auto",
        " console-setup/ask_detect=false",
        " console-setup/layoutcode=us",
        " console-setup/modelcode=pc105",
        " debconf/frontend=noninteractive",
        " debian-installer=en_US",
        " fb=false",
        " initrd=/install/initrd.gz",
        " kbd-chooser/method=us",
        " keyboard-configuration/layout=USA",
        " keyboard-configuration/variant=USA",
        " locale=en_US",
        " netcfg/get_domain=vm",
        " netcfg/get_hostname=packer",
        " noapic",
        " preseed/url=http://{{ .HTTPIP }}:{{ .HTTPPort }}/preseed.cfg",
        " -- ",
        "<enter>"
      ]
    }
  ]
}

preseed.cfg

choose-mirror-bin mirror/http/proxy string
d-i base-installer/kernel/override-image string linux-server
d-i clock-setup/utc boolean true
d-i clock-setup/utc-auto boolean true
d-i finish-install/reboot_in_progress note

# Partitions
d-i grub-installer/only_debian boolean true
d-i grub-installer/with_other_os boolean true
d-i partman-auto-lvm/guided_size string max
d-i partman-auto/choose_recipe select atomic
d-i partman-auto/method string lvm
d-i partman-lvm/confirm boolean true
d-i partman-lvm/confirm boolean true
d-i partman-lvm/confirm_nooverwrite boolean true
d-i partman-lvm/device_remove_lvm boolean true
d-i partman/choose_partition select finish
d-i partman/confirm boolean true
d-i partman/confirm_nooverwrite boolean true
d-i partman/confirm_write_new_label boolean true

# Users
d-i passwd/user-fullname string packer
d-i passwd/user-uid string 500
d-i passwd/user-password password packer
d-i passwd/user-password-again password packer
d-i passwd/username string packer

# Packages
d-i pkgsel/install-language-support boolean false
d-i pkgsel/update-policy select unattended-upgrades
d-i pkgsel/upgrade select full-upgrade
d-i pkgsel/include string openssh-server

d-i time/zone string UTC
d-i user-setup/allow-password-weak boolean true
d-i user-setup/encrypt-home boolean false
tasksel tasksel/first multiselect standard, ubuntu-server