Archaeologist·Field Notes from axolotl-ai-cloud/axolotl
Vol. I · Field Notes

axolotl-ai-cloudaxolotl

LLM Trainer

9 May 2026·a sprawling project
Reading Posture
From the Field
The de facto standard for open-source LLM fine-tuning, but not for beginners.
Verdict:Reach for it
Reach for it when

You need to fine-tune a large language model with maximum flexibility and community support.

Look elsewhere when

You want a plug-and-play GUI or are fine-tuning a small model for a simple task.

In context

It's like Hugging Face's TRL but with far more built-in optimizations and a steeper learning curve.

Complexity●●●Heavy
Read time~30 minutes
Language
Python
Runtime
Python >=3.10
Dependencies
0total

What using it looks like

Drawn from the project's README

From the README
# install uv if you don't already have it installed (restart shell after)
curl -LsSf https://astral.sh/uv/install.sh | sh

# change depending on system
export UV_TORCH_BACKEND=cu128

# create a new virtual environment
uv venv --python 3.12
source .venv/bin/activate

uv pip install torch==2.10.0 torchvision
uv pip install --no-build-isolation axolotl[deepspeed]

# Download example axolotl configs, deepspeed configs
axolotl fetch examples
axolotl fetch deepspeed_configs  # OPTIONAL
Fig. 1 — example 1 of 5

What this is

As told for the tourist

What Is This?

Axolotl is a free, open-source tool that lets you take an existing AI model (like one of Meta's Llama models) and teach it new skills or knowledge using your own data. Think of it as a personal trainer for AI — you bring the raw model and the example material, and Axolotl handles the heavy lifting of actually running the "workout" sessions.

What Can You Do With It?

You could use this to make a general-purpose AI model become an expert in your company's internal documentation, or teach it to write code in your team's specific style. For example, after installing Axolotl, you could run:

axolotl fetch examples

axolotl train examples/llama-3/lora-1b.yml

The first command downloads ready-made training recipes, and the second starts the actual teaching process. You could also spin up a pre-configured environment with Docker (a way to run software in isolated containers) using:

docker run --gpus '"all"' --ipc=host --rm -it axolotlai/axolotl:main-latest

This gives you a complete training workshop without installing anything on your own computer.

axolotl fetch examples
axolotl train examples/llama-3/lora-1b.yml
docker run --gpus '"all"' --ipc=host --rm -it axolotlai/axolotl:main-latest

How It Works (No Jargon)

1. The Recipe Book (Configuration Files)

You write a simple text file (like a recipe) that says which model to use, what data to train on, and how aggressively to train. Axolotl reads this recipe and sets everything up automatically — it's like giving a chef a recipe card instead of having to explain every step.

2. The Training Loop (Repetition with Feedback)

The core process is like a student doing practice problems. The model tries to answer, checks its answer against the correct one you provided, then adjusts slightly. Axolotl runs this loop thousands of times, gradually making the model better at your specific task. It's like learning to throw a basketball — you miss, adjust your form, try again, and slowly improve.

3. The Efficiency Tricks (Memory Management)

Large AI models are like enormous libraries — they take up huge amounts of memory. Axolotl uses clever techniques (like "LoRA," which is like only rewriting the index cards instead of the whole library) to make training possible on normal computers. It also uses special math shortcuts (called "kernels") that run calculations faster, like using a calculator instead of doing long division by hand.

What's Cool About It?

The project is named after the axolotl, a salamander that can regrow lost body parts. Similarly, this tool lets you "regrow" parts of an AI model — you can add new capabilities without starting from scratch. It's also designed to work with many different model types (Llama, Mistral, Gemma, etc.) using the same simple commands, so you don't need to learn a new system for each model.

Who Should Care?

Reach for this if: You have a specific AI model you want to customize for your own data, you're comfortable running commands in a terminal, and you want a tool that handles the messy details of GPU memory management and training optimization for you.

Skip it if: You just want to use a pre-trained model through a web interface (like ChatGPT), or you're not ready to install software and manage files on your computer. Also skip if you need to train models from absolute scratch — Axolotl is designed for fine-tuning existing models, not building new ones from zero.

Start Here

A recommended reading path through the code

Start Here

A recommended reading path through the code

  1. 01

    Reveals the package's public API surface and versioning, establishing the top-level namespace.

  2. 02

    Defines core data abstractions (SFTDataset, DPODataset, etc.) that are central to how the codebase handles training data.

  3. 03

    Exposes the TRL trainer configuration models, critical for understanding reinforcement learning integration.

  4. 04

    Demonstrates the training loop extension mechanism via callbacks, revealing how monitoring and checkpointing work.

  5. 05

    Empty init file that signals the monkeypatching pattern used to modify transformers behavior, a key architectural approach.

What's inside

15 sections of the codebase

Read Next

Where to go from here

📰
Article2024

Fine-Tuning LLMs with Axolotl: A Beginner's Guide

Hugging Face Blog

Provides a gentle, hands-on introduction to using Axolotl for fine-tuning, explaining key concepts without assuming deep ML knowledge.

📺
Video2024

Axolotl: The Ultimate LLM Fine-Tuning Tool

YouTube (Sam Witteveen)

A clear walkthrough of setting up and running Axolotl, showing the practical steps and common pitfalls for newcomers.

📰
Article2023

What is QLoRA? Efficient Fine-Tuning of Quantized LLMs

Hugging Face Blog

Explains the core technique behind Axolotl's memory-efficient fine-tuning, making the project's optimizations understandable.

📰
Article2024

A Beginner's Guide to Fine-Tuning LLMs

MLOps Community Blog

Covers the high-level workflow of LLM fine-tuning, giving context for why Axolotl's features matter.

Sibling Projects

Codebases that occupy adjacent space

Related Expeditions
axolotl🤗TRLUnsloth💬FastChat🦎Axolotl (self)
 

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Words You'll Hear

Hover the dotted terms above for definitions in context

attention mechanism

concept

A key component in many AI models that allows the model to focus on the most relevant parts of the input data when generating an output, like focusing on certain words in a sentence.

bitsandbytes

library

A library that provides efficient implementations of quantization and other low-precision operations for training and running large models on GPUs.

distributed training

concept

A technique for training large AI models by splitting the work across multiple computers or GPUs to speed up the process and handle larger models.

DPO

pattern

Stands for Direct Preference Optimization, a simpler alternative to RLHF that directly optimizes a model based on pairs of preferred and non-preferred outputs.

fine-tuning

concept

The process of taking a pre-trained AI model and training it further on a smaller, specific dataset to adapt it for a particular task or domain.

Flash Attention

pattern

A fast and memory-efficient implementation of the attention mechanism that speeds up training and inference by reducing memory reads and writes.

FSDP

pattern

Stands for Fully Sharded Data Parallelism, a method that splits a model's parameters across multiple GPUs to train very large models that wouldn't fit on a single GPU.

FSDP2

pattern

An updated version of FSDP that improves efficiency and ease of use for sharding model parameters across multiple GPUs during training.

GRPO

pattern

Stands for Group Relative Policy Optimization, a reinforcement learning algorithm used to fine-tune language models by comparing groups of generated outputs.

HuggingFace Transformers

library

A popular open-source library that provides pre-trained models and tools for natural language processing tasks, like text generation and classification.

importance sampling

concept

A statistical technique used in reinforcement learning to correct for the difference between the policy that generated data and the current policy being trained.

kernel

concept

A small, optimized piece of code that runs on a GPU to perform a specific mathematical operation very efficiently, often used for speeding up AI computations.

KL divergence

concept

A mathematical measure of how different two probability distributions are, often used in AI to prevent a model's updated version from straying too far from its original behavior.

LLM

concept

Stands for Large Language Model, a type of AI model trained on massive amounts of text data to understand and generate human-like language.

LoRA

pattern

Stands for Low-Rank Adaptation, a technique for fine-tuning large models by adding small, trainable matrices to existing layers, which is much more memory-efficient than full fine-tuning.

MoE

concept

Stands for Mixture of Experts, a model architecture that uses multiple specialized sub-networks (experts) and a router to activate only a few of them for each input, saving computation.

monkeypatch

pattern

A programming technique where you replace or modify parts of a library's code at runtime, without changing the original source files, to alter its behavior.

Pydantic

library

A Python library for data validation and settings management that uses Python type hints to define and enforce the structure and constraints of data.

QLoRA

pattern

A memory-saving technique that combines quantization (reducing number precision) with LoRA (a method for efficient fine-tuning) to train large models on a single consumer GPU.

quantization

concept

A technique that reduces the precision of numbers used in a model (e.g., from 32-bit to 4-bit) to make it smaller and faster, often with minimal loss in quality.

ring attention

pattern

A technique for sequence parallelism where attention computation is distributed across multiple GPUs arranged in a ring, allowing processing of very long sequences.

RLHF

concept

Stands for Reinforcement Learning from Human Feedback, a training method where a model learns from feedback given by humans to better align its outputs with human preferences.

Triton

tool

A programming language and compiler designed to make it easier to write custom, high-performance GPU kernels for deep learning.

TRL

library

Stands for Transformer Reinforcement Learning, a library built on top of HuggingFace Transformers for training language models using reinforcement learning.

vLLM

library

A high-performance library for running large language model inference, designed to be fast and memory-efficient, often used for serving models in production.