Trivial Debian preseed templater

To simplify Debian automated installation with preseed, and to make it more manageable, this is my personal, trivial, and definitely ugly, tiny tool.

It helps me to manage multiple preseed templates, each belongs to a host group. Hopefully, it can help you, too.

How-to

1. Create a new template for your host group,

   ./preseeder -t homelab

2. That will generate two template files:

   • tmpl/homelab/preseed.cfg.tmpl
   • tmpl/homelab/latecmd.sh.tmpl

   Edit them to match your needs.

3. Extract all variables used in those template files,

   ./preseeder -e homelab

4. That will generate a starter variable file vars/homelab/var.

   Copy or rename it to match your planned installation, e.g.,

   mv vars/homelab/var vars/homelab/host-01

5. Edit the variable file to match your infrastructure, e.g.,

   DOMAIN="home.lab"
   HOSTNAME="host-01"
   FULLNAME="Debian Admin"
   GH_USERNAME="geekobiloba"
   KEYBOARD="us"
   LOCALE="id_ID.utf8"
   TIMEZONE="Asia/Jakarta"
   MIRROR_COUNTRY="Indonesia"
   PACKAGES="build-essential git curl jq htop vim ripgrep bat"
   FILESYSTEM="ext4"
   USERNAME="geekobiloba"
   PASSWD_HASH_USER='$6$RXZ9ccXz07zIlcWK$Q5HMTePavdX9L9HBQWrQtQLcaD6Qz8494CdCBsaPqtfJJVebrGspSYeAFx15X5RzBhdg0rGywEuiqgn4LQ.kW0'
   PASSWD_HASH_ROOT='$6$RXZ9ccXz07zIlcWK$Q5HMTePavdX9L9HBQWrQtQLcaD6Qz8494CdCBsaPqtfJJVebrGspSYeAFx15X5RzBhdg0rGywEuiqgn4LQ.kW0'
   NTP_SERVER="time.bmkg.go.id"
   LATECMD_URL="http://192.168.111.111:8000/homelab/host-01/latecmd.sh"

   You can create hashed passwords with openssl passwd -6.

6. Optionally, copy and edit the variable file for other hosts under the same group, each file for a single host.

7. Then, make preseed files for the whole host group.

   ./preseeder -p homelab

   Your final directory structure should resemble this,

   .
   ├── preseed
   │   └── homelab
   │       ├── host-01
   │       │   ├── latecmd.sh
   │       │   └── preseed.cfg
   │       └── host-02
   │           ├── latecmd.sh
   │           └── preseed.cfg
   ├── preseeder
   ├── tmpl
   │   ├── default
   │   │   ├── latecmd.sh.tmpl
   │   │   └── preseed.cfg.tmpl
   │   └── homelab
   │       ├── latecmd.sh.tmpl
   │       └── preseed.cfg.tmpl
   └── vars
       └── homelab
           ├── host-01
           └── host-02
   

Using the preseed

The straightforward way is to deliver them via HTTP.

1. Serve the preseed directory with Python,

   python3 -m http.server -d preseed

2. Run an ordinary Debian installer, choose Advanced options, then Automated install.

   Wait until a prompt titled Download debconf preconfiguration file appears, then enter http://${WEB_SERVER_IP}:8000/homelab/host-01/preseed.cfg.

   The installer will continue unattendedly to finish, unless there's an error, of course.

Other options are listed here, or using a DHCP server.

FAQs

• Why bother with preseed when there's Ansible?

  Ansible runs post-installation, and it can't give answers to the installer. Besides, preseed is there with every Debian installer since like forever.

• Why not cloud-init?

  Then I'll have to use the Debian cloud images, which give me only a few architectures.

• How do you use this mostly?

  Automating Debian installation on niche archs, like ARMv7 or MIPSel, mostly on QEMU, to compile stuff for embedded devices, usually runs OpenWrt.

• Is there any caveats?

  Yes. This tool doesn't check preseed files validity. You should know what you're doing when authoring them.

  Read the official docs and partition recipe to learn more.