Debian-builder

Utility to embed the preseed.cfg file into the Debian NetInstall image.

Overview

RedHat has Kickstart, SuSE has AutoYaST and Debian has a preseed.cfg file to automate operating system installations. You can either attach a second drive to your machine while installing and manually tell the installer where the file is located, or you can burn the preseed.cfg file into the ISO image. (See here and here.)

All the options are slightly cumbersome. This utility automates the process of embedding your preseed.cfg into an ISO image. You just have to write your own preseed. And know how to run Docker...

How to use

After installing Docker to your favorite operating system and creating your preseed file, you run the following command in the folder where you put your preseed.cfg.

docker run -it --rm -v $(pwd):/mnt freshautomations/debian-builder

The execution will show you Docker downloading the Debian netinstaller, unpacking it, adding your preseed file as well as making changes to the boot loader so the file is automatically loaded. Then it recompiles the ISO file. At the end you will see a few new files in your file system:

• debian-11.6.0-amd64-netinst.iso or similar: the downloaded official netinstaller.
• debian-11.6.0-amd64-custom.iso: the customized netinstaller ISO that contains and executes the preseed file.

Burn the custom ISO to a CD, DVD or USB stick with your favorite application. My current favorite is balenaEtcher because it works so well on my macOS.

Custom configuration

• If you already have the official ISO downloaded in your folder, it will automatically will be used and it will not be re-downloaded. In this case it's the user's responsibility to make sure that the ISO is valid.
• You can add -e VERSION=11.6.0 environment variable to the docker execution to download a different Debian version.
• You can add -e NAME=custom environment variable that will be used to name the output image. (Well the last section of it.)
• You can add -e TIMEOUT=5 environment variable that will be used to set the bootloader menu timeout in seconds.
• You can add -e NOMODESET=1 environment variable that will be used to disable graphics card acceleration for the installer. (Unset by default.)

I don't have Docker

Docker is only used to simplify the environment setup. You can run the embedded script without Docker, if you set up your own environment. The main components:

• Install xorriso in your environment. This is used unpack/repack the ISO image.
• Download the Official Debian Netinstall image or have wget, sha512sum and gnupg installed so the script can download and verify it for you.
• Have a generic set of Linux commands available: cpio, sed, md5sum, gzip/gunzip, find, dd.

Additional environment variables are available to configure the script:

• DEBUG=1 will enable tracing the script line-by-line as well as not removing some temporary files. (Unset by default.)
• MNT=/mnt will tell the script where the input files (preseed.cfg and optionally an official ISO image) are located on the file system
• MEDIA=/media will tell the script where to expand the official ISO image.
• TMP=/tmp will mount the temporary folder somewhere else.
• FORCE=1 will force ALL the boot menu items to be automated installations with the preseed.cfg set. If this is not set, only the "Automated ..." items are set and the boot menu defaults to the automated graphical installation. (Unset by default.)