How to avoid interactive dialogs when running "apt-get upgrade -y" in Ubuntu 16.04 when packaging with Packer?

I'm using Packer to create an AWS AMI based on an Ubuntu 16.04 image. In the beginning, I'm doing an upgrade:

sudo apt-get update
sudo apt-get upgrade -y

Here is the relevant part of my provisioners section:

"provisioners": [
  {
    "type": "shell",
    "inline": [
      "sudo apt-get update",
      "sudo apt-get upgrade -y"
    ]
  }
]

This breaks the automatization, however, as an interactive dialog pops up:

amazon-ebs: Found kernel: /boot/vmlinuz-4.4.0-72-generic
amazon-ebs: A new version of /boot/grub/menu.lst is available, but the version installed
amazon-ebs: currently has been locally modified.
amazon-ebs:
amazon-ebs: 1. install the package maintainer's version
amazon-ebs: 2. keep the local version currently installed
amazon-ebs: 3. show the differences between the versions
amazon-ebs: 4. show a side-by-side difference between the versions
amazon-ebs: 5. show a 3-way difference between available versions
amazon-ebs: 6. do a 3-way merge between available versions (experimental)
amazon-ebs: 7. start a new shell to examine the situation

I also tried to set export DEBIAN_FRONTEND=noninteractive before (as recommended in this answer). Unfortunately, it makes no difference.

Questions:

• Is there a way to get past the iteractive dialog (selecting option 1 would be fine)?

• Is it instead better to avoid upgrades and instead trust that the AMIs are up to date and contain the critical security patches?

Background: This is the relevant part of my "builders" section, where I configured it to use the latest available AMI:

"builders": [{
  "type": "amazon-ebs",
  "region": "eu-central-1",
    ...
    "source_ami_filter": {
        "filters": {
            "virtualization-type": "hvm",
            "name": "*ubuntu-xenial-16.04-amd64-server-*",
            "root-device-type": "ebs"
        },
        "owners": ["099720109477"],
        "most_recent": true
    },
  ...
}]

Note: Turns out that the noniteractive mode works if you

This sequence of commands works for me:

apt-get update
DEBIAN_FRONTEND=noninteractive apt-get upgrade -yq

So, DEBIAN_FRONTEND=noninteractive is correct but you also need the -q flag.

Source: https://github.com/moby/moby/issues/4032

StackExchange DevOps Q#1139, answer score: 26