---
page_title: Unattended Debian/Ubuntu Installation
description: |-
  Learn how to use a preseed file to automatically answer installation
  questions and enable Packer to connect to your Debian instance.
---

# Unattended Installation for Debian

Unattended Debian/Ubuntu installation is done via "preseed" files

These files are generally named "preseed.cfg". They are not
Packer-specific tools, though we do make use of them.

If, after following this guide, you're still having issues getting a preseed
file working, We recommend you read the official documentation on
[preseed files](https://wiki.debian.org/DebianInstaller/Preseed).

The guide here is hopefully enough to get you started, but isn't a replacement
for the official documentation.

## When To Use a Preseed File

If you are installing the operating system from a mounted iso as part of
your Packer build, you will need to use a preseed file. For example, you're
building an image from scratch using the [vmware-iso](/docs/builders/vmware-iso),
[virtualbox-iso](/docs/builders/virtualbox-iso), or
[hyperv-iso](/docs/builders/hyperv-iso) builders.

If you are not installing the operating system, you won't need to provide a
preseed file. If you are using a pre-built image in a cloud, you don't need to
worry about preseed files.

## How to make a Preseed File

You can either start from an example preseed file from a known repo (take a look
at the examples links below), or you can start with the official [example
preseed](https://www.debian.org/releases/stable/example-preseed.txt), and
comment or uncomment the options as you need them.

## Where to put the preseed file

The `-iso` builders mentioned above all have an `http_dir` or an `http_content`
option. Any file inside of your `http_dir` or `http_content` will be served on a
local fileserver for your virtual machine to be able to access. One very common
use for this directory is to use it to provide your preseed file.

You then reference the file using a `boot_command` to kick off the installation.
In the example below, see how the `preseed/url` command line option is being
used in the `/install/vmlinuz command`. The `{{ .HTTPIP }}` and
`{{ .HTTPPort }}` options are special Packer template options that will get set
by Packer to point to the http server we create, so that your boot command can
access it. For an example of a working boot_command, see the Examples section
below. For more information on how boot_command works, see the
boot_command section of the docs for whatever builder you are using.

## What does Packer _need_ the preseed file to do?

Packer needs the preseed file to handle any questions that would normally be
answered interactively during a Debian installation.

If you want to be able to use provisioners, the preseed file must also install
SSH so that Packer can connect to the instance.

## Examples

A very minimal example of a preseed file can be found below. Much of this was
copied from the official example-preseed shared above. Notice that we are
installing ssh via `d-i pkgsel/include string openssh-server` and configuring
a username so that Packer will be able to connect.

You need to make sure that your mirror settings are properly configured for your
specific distribution of Debian.

```shell
# Preseeding only locale sets language, country and locale.
d-i debian-installer/locale string en_US

# Keyboard selection.
d-i console-setup/ask_detect boolean false
d-i keyboard-configuration/xkb-keymap select us

choose-mirror-bin mirror/http/proxy string

### Clock and time zone setup
d-i clock-setup/utc boolean true
d-i time/zone string UTC

# Avoid that last message about the install being complete.
d-i finish-install/reboot_in_progress note

# This is fairly safe to set, it makes grub install automatically to the MBR
# if no other operating system is detected on the machine.
d-i grub-installer/only_debian boolean true

# This one makes grub-installer install to the MBR if it also finds some other
# OS, which is less safe as it might not be able to boot that other OS.
d-i grub-installer/with_other_os boolean true

### Mirror settings
# If you select ftp, the mirror/country string does not need to be set.
d-i mirror/country string manual
d-i mirror/http/directory string /ubuntu/
d-i mirror/http/hostname string archive.ubuntu.com
d-i mirror/http/proxy string

### Partitioning
d-i partman-auto/method string lvm

# This makes partman automatically partition without confirmation.
d-i partman-md/confirm boolean true
d-i partman-partitioning/confirm_write_new_label boolean true
d-i partman/choose_partition select finish
d-i partman/confirm boolean true
d-i partman/confirm_nooverwrite boolean true

### Account setup
d-i passwd/user-fullname string vagrant
d-i passwd/user-uid string 1000
d-i passwd/user-password password vagrant
d-i passwd/user-password-again password vagrant
d-i passwd/username string vagrant

# The installer will warn about weak passwords. If you are sure you know
# what you're doing and want to override it, uncomment this.
d-i user-setup/allow-password-weak boolean true
d-i user-setup/encrypt-home boolean false

### Package selection
tasksel tasksel/first standard
d-i pkgsel/include string openssh-server build-essential
d-i pkgsel/install-language-support boolean false

# disable automatic package updates
d-i pkgsel/update-policy select none
d-i pkgsel/upgrade select full-upgrade
```

Here's an example of the vmware-iso builder being used to call this preseed.
In this case, it is assumed that the file is saved as preseed.cfg inside of a
directory called "http", and Packer is being called from the directory
containing the "http" directory.

```hcl
  "builders": [
    {
      "boot_command": [
        "<esc><wait>",
        "<esc><wait>",
        "<enter><wait>",
        "/install/vmlinuz<wait>",
        " initrd=/install/initrd.gz",
        " auto-install/enable=true",
        " debconf/priority=critical",
        " preseed/url=http://{{ .HTTPIP }}:{{ .HTTPPort }}/preseed_2.cfg<wait>",
        " -- <wait>",
        "<enter><wait>"
      ],
      "boot_wait": "10s",
      "guest_os_type": "ubuntu-64",
      "http_directory": "http",
      "iso_checksum": "file:///Users/mmarsh/dev/repro_cases/packer_cache/shasums.txt",
      "iso_url": "http://old-releases.ubuntu.com/releases/14.04.1/ubuntu-14.04.1-server-amd64.iso",
      "shutdown_command": "echo 'vagrant' | sudo -S shutdown -P now",
      "ssh_password": "vagrant",
      "ssh_username": "vagrant",
      "ssh_wait_timeout": "10000s",
      "tools_upload_flavor": "linux",
      "type": "vmware-iso"
    }
  ],
```

For more functional examples of a debian preseeded installation, you can see the
Chef-maintained bento boxes for [Debian](https://github.com/chef/bento/tree/master/packer_templates/debian)
and [Ubuntu](https://github.com/chef/bento/tree/master/packer_templates/ubuntu)
