---
title: "Chapter 02: Train an Adapter"
description: "Build a 15–20 image Dreambooth dataset with a trigger token and run your first mflux training from a JSON config."
type: lesson
order: 2
chapter: "01-lora-eyes-open"
---

# Chapter 02: Train an Adapter

## The Dataset

15–20 images of one subject. A person, an object, a place. Pick something you have a lot of photos of and **can judge quality on instantly** — that instant judgment is the whole point of doing images first.

- Consistent subject, varied background/lighting/angle
- 512×512 (mflux's training default)
- Captions using a rare trigger token (`TOK`, `sks`, whatever) so the model binds the concept to a handle it isn't already using

## Training

Dreambooth training in mflux is driven **entirely by a JSON config** — training parameters cannot be passed as CLI flags. Start from the bundled example:

```bash
cd mflux
mflux-train --train-config src/mflux/dreambooth/_example/train.json
```

Copy that config, point it at your dataset, edit the `examples` section. Default is 512×512, batch size 1.

Expect several hours for a full run depending on machine and step count. Use `--low-ram` if memory pressure goes yellow — it constrains the MLX cache and releases the text encoders and transformer components after use.

## While It Trains

Read the mflux source (Chapter 01's homework). Or write down your predictions: what do you expect rank 64 on 5 images to produce? What about 2000 steps on 15 images? You'll check these predictions in Chapter 03.

## Known Failure Modes

- **"None of my LoRAs look good."** Known territory — early Dreambooth-on-MLX results were widely reported as poor, and adapters trained in one tool didn't always load in another. Don't over-index on quality; you're here for the *deltas between runs*, not a shippable adapter.
- **Slowdowns after interleaving generation with training.** Documented issue. Train, then generate. Don't interleave.

---

[← Chapter 01](/fine-tune-local-agent/01-lora-eyes-open/01-why-images-first/) · [Next: Chapter 03 →](/fine-tune-local-agent/01-lora-eyes-open/03-the-experiments/)