Fine-tune Llama 3.1 with LoRA using Soup CLI

This guide shows how to fine-tune Meta Llama 3.1 8B with LoRA adapters on a custom dataset using Soup CLI. End-to-end from install to inference in under 10 minutes on a single GPU.

Why LoRA on Llama 3.1?

LoRA (Low-Rank Adaptation) trains only a small fraction (~0.1%) of model parameters, which means:

  • Train 8B parameter Llama 3.1 on a single 24GB GPU (RTX 4090, A10)
  • Checkpoints are tiny (~100MB instead of 16GB)
  • Faster training and easier experimentation

1. Install

bash
pip install "soup-cli[train,fast]"

Since v0.71.0 the base soup-cli package is a light, PyTorch-free CLI. [train] adds the training stack; [fast] adds Unsloth on top. Installing [fast] alone cannot train.

The [fast] extra adds Unsloth for 2–5× training speedup on Llama-family models.

2. Prepare your dataset

Use the Alpaca format (JSON list of instruction/input/output triples):

json
[
  {
    "instruction": "Summarize the following text.",
    "input": "Soup CLI is a fine-tuning toolkit...",
    "output": "Soup CLI is an open-source LLM fine-tuning tool."
  }
]

Save as train.json.

3. Create the config

Save as llama31.yaml:

yaml
base: meta-llama/Llama-3.1-8B-Instruct
task: sft
backend: unsloth            # root-level, NOT under training

data:
  train: train.json
  format: alpaca
  max_length: 2048          # sequence length lives under data

training:
  epochs: 3
  lr: 2.0e-4                # the key is lr, not learning_rate
  batch_size: 2
  gradient_accumulation_steps: 8
  lora:
    r: 16                   # LoRA turns on when r > 0; there is no enabled flag
    alpha: 32
    dropout: 0.05
    target_modules: [q_proj, k_proj, v_proj, o_proj]

output: ./runs/llama31

Config keys are validated, but unknown keys are ignored rather than rejected. Writing learning_rate instead of lr, or nesting backend under training, does not raise: the value is silently dropped and the default is used instead. If a setting seems to have no effect, check the spelling against Configuration first.

4. Train

bash
soup train --config llama31.yaml

Soup auto-detects GPU, enables FlashAttention, and trains LoRA adapters. Expect ~20 minutes for 1k examples on an RTX 4090.

5. Chat with your fine-tuned model

bash
soup chat --model ./runs/llama31/latest

6. Export for deployment

bash
# Merge LoRA into base model and export GGUF for Ollama
soup export --model ./runs/llama31/latest --format gguf --quant q4_k_m

Troubleshooting

Out of memory? Enable QLoRA (a 4-bit base model). Note 4bit is already the default, so this is only worth setting explicitly if you changed it:

yaml
training:
  quantization: 4bit
  lora:
    r: 16

Slow training? Ensure backend: unsloth is set at the root of the config (not under training) and that you installed pip install "soup-cli[train,fast]".

Next steps

Soup is free and Apache-2.0. If it saved you a training run, starring the repo costs nothing and helps most. You can also fund the GPU time behind the work a 4 GB laptop cannot reach.