[issue]: Debian Preseed Barfs at NetCFG WHATEVER I put in Preseed

Official FAQ

• I have checked the official FAQ.

Ventoy Version

1.0.15

What about latest release

Yes. I have tried the latest release, but the bug still exist.

Try alternative boot mode

No. I didn't try these alternative boot modes.

BIOS Mode

UEFI Mode

Partition Style

GPT

Disk Capacity

256GB

Disk Manufacturer

Kingson NVME

Image file checksum (if applicable)

None

Image file download link (if applicable)

No response

What happened?

Debian netinst preseed injection via auto_install causes "Invalid Passphrase" WiFi error

Environment

• Ventoy version: 1.0.15
• ISO: debian-13.6.0-amd64-netinst.iso
• Preseed method: auto_install plugin with template .cfg files
• Testing platform: Dell Latitude 3140 (no Ethernet present)

Description

When using Ventoy's auto_install plugin to inject preseed configuration files into Debian 13 netinst installation, the installer fails at the "Configure the Network" stage with an "Invalid Passphrase" error for WiFi networks.

The same preseed files work correctly when:

• Plain Debian netinst is used without any preseed (prompts normally for network configuration and completes successfully)

Steps to Reproduce

1. Create a preseed .cfg file containing only locale, account, package, and disk settings (NO network configuration)
2. Configure ventoy.json with auto_install plugin pointing to the preseed template file
3. Boot Debian 13 netinst from Ventoy and select a desktop environment template from the auto_install menu
4. Observe installer behavior

Expected Behavior

Preseed injection via auto_install should not alter d-i's (Debian Installer) network detection/configuration behavior. If the preseed file contains no network configuration directives, d-i should behave identically to a plain netinst boot, allowing users to manually select and configure their network interface.

Actual Behavior

• d-i detects network hardware
• Installer moves to "Configure the Network" stage
• d-i attempts automatic WiFi connection with an unknown passphrase
• Installer fails with "Invalid Passphrase" error
• Installation is blocked and cannot proceed

Control Test Results

Without Ventoy preseed: Plain Debian 13 netinst boots normally, allows user to manually select network interface (Ethernet or WiFi), prompts for WiFi credentials when needed, and installation completes successfully.

With Ventoy preseed (even with zero network config in preseed file): Same "Invalid Passphrase" error occurs, blocking installation.

Additional Notes

• The preseed file contains no d-i netcfg/* directives whatsoever
• Keyboard configuration preseed directives ARE applied correctly (confirming preseed is being read)
• The error occurs identically in both graphical and text-based installers
• The error occurs identically regardless of whether timeouts or other netcfg settings are added to the preseed

Suspected Root Cause

Ventoy's preseed injection mechanism may be modifying or interfering with d-i's network detection initialization, causing d-i to attempt automatic connection with incorrect or uninitialized credentials, rather than prompting the user for manual network configuration.