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Understanding Modelfile in Ollama

Understanding the Ollama Modelfile: A Guide for Developers

Ollama, known for its tools designed to streamline coding and model development processes, introduces an essential tool in this endeavor: the Modelfile. This guide aims to elucidate the structure, utility, and application of the Ollama Modelfile, ensuring developers can leverage this resource to its fullest potential.

The Essence of the Modelfile

At its core, the Modelfile serves as a blueprint for creating and sharing models within the Ollama ecosystem. It’s designed with simplicity and flexibility in mind, allowing developers to define the parameters, system messages, templates, and other essential components that make up a model. Whether you’re looking to build from an existing model or start from scratch, the Modelfile provides a structured yet adaptable framework to do so.

Deciphering the Modelfile Format

The Modelfile adopts a straightforward syntax that emphasizes readability and ease of use:

# comment

Each instruction within the file serves a distinct purpose, from specifying the base model with FROM to setting up model parameters via PARAMETER. Here’s a quick overview of the key instructions:

  • FROM: Identifies the base model. This is mandatory for defining the foundation upon which your model is built.
  • PARAMETER: Allows for the customization of model behavior through various settings.
  • TEMPLATE: Defines the prompt template sent to the model, incorporating optional variables for dynamic responses.
  • SYSTEM, ADAPTER, LICENSE, MESSAGE: These instructions further refine the model’s operation, integrating system messages, adapters for QLoRA, legal licenses, and preset message histories.

Understanding PARAMETERS

Parameteres plays an important role in how the model would respond to your queries, defining paramaters is not an easy task and this would take a lot of trial and error to perfect, lets understand these to use them efficiently.


  • What It Does: Like a volume control for the machine’s “creativity.” Turning it on makes the machine’s responses less predictable.
  • Example: PARAMETER mirostat 1 (0 is off, 1 is on, 2 is extra on).


  • What It Does: Adjusts how quickly the machine learns from what it’s currently talking about. Turning it down makes it more cautious; turning it up makes it adapt faster.
  • Example: PARAMETER mirostat_eta 0.1


  • What It Does: Helps decide if the machine should stick closely to the topic (lower values) or explore a bit more creatively (higher values).
  • Example: PARAMETER mirostat_tau 5.0


  • What It Does: Determines how much of the previous conversation the machine can remember at once. Larger numbers mean it can remember more of what was said earlier.
  • Example: PARAMETER num_ctx 4096


  • What It Does: Like tuning how many different tasks the machine can juggle at once. Important for very complex models.
  • Example: PARAMETER num_gqa 8


  • What It Does: Sets how many “brains” (or parts of the computer’s graphics card) the machine uses to think. More brains can mean faster or more detailed thinking.
  • Example: PARAMETER num_gpu 50


  • What It Does: Determines how many separate conversations or tasks the machine can handle at the same time. Like opening more lanes on a highway.
  • Example: PARAMETER num_thread 8


  • What It Does: This is like telling the machine how much of the last part of the conversation to try not to repeat, keeping the chat fresh.
  • Example: PARAMETER repeat_last_n 64


  • What It Does: If the machine starts repeating itself, this is like a nudge to encourage it to come up with something new.
  • Example: PARAMETER repeat_penalty 1.1


  • What It Does: Controls how “wild” or “safe” the machine’s responses are. Higher temperatures encourage more creative responses.
  • Example: PARAMETER temperature 0.7


  • What It Does: Sets up a starting point for generating responses. Using the same seed number with the same prompt will always give the same response.
  • Example: PARAMETER seed 42


  • What It Does: Tells the machine when to stop talking, based on certain cues or keywords. It’s like saying “When you hear this word, it’s time to wrap up.”
  • Example: PARAMETER stop "AI assistant:"


  • What It Does: Aims to reduce randomness in the machine’s responses, keeping its “thoughts” more focused.
  • Example: PARAMETER tfs_z 2.0


  • What It Does: Limits how much the machine can say in one go. Setting a limit helps keep its responses concise.
  • Example: PARAMETER num_predict 128


  • What It Does: Limits the machine’s word choices to the top contenders, which helps it stay on topic and make sense.
  • Example: PARAMETER top_k 40


  • What It Does: Works with top_k to fine-tune the variety of the machine’s responses, balancing between predictable and diverse.
  • Example: PARAMETER top_p 0.9

Adjusting these parameters is like tuning an instrument or setting up a complex piece of equipment for a specific job. Each one influences a different aspect of how the machine thinks, remembers, and communicates, allowing you to customize its behavior to suit your needs, much like setting up a video game character with different skills and attributes for different types of challenges.

Implementing a Basic Modelfile

Consider the task of creating a Mario-themed assistant. The Modelfile might look something like this:

FROM llama2
PARAMETER temperature 1
PARAMETER num_ctx 4096
SYSTEM You are Mario from super mario bros, acting as an assistant.

This example demonstrates setting the base model, adjusting creativity and context window size through parameters, and specifying a custom system message to guide the assistant’s behavior.

Utilizing Modelfiles from Ollama’s Library

Ollama’s library provides a wealth of Modelfiles for different applications, from simple assistants to more complex models. Accessing these files can inspire your creations or serve as a direct foundation for your projects. The ollama show command is particularly useful for displaying the Modelfile of any local model, offering insights into its configuration and potentially serving as a template for your custom models.

Practical Tips for Modelfile Creation

  • Start with a Base Model: Use the FROM instruction to specify your starting point. This can be a model from Ollama’s library or a custom bin file.
  • Customize Parameters: Tailor the model’s behavior to your needs with the PARAMETER instruction. Experiment with different settings to find the optimal configuration.
  • Define Interaction Templates: Use the TEMPLATE instruction to craft how the model will interact with prompts, including system messages and user queries.
  • Incorporate Adapters and Licenses as Needed: If your model requires specific adapters or needs to adhere to certain license conditions, use the ADAPTER and LICENSE instructions to include these in your Modelfile.
  • Test and Iterate: The creation of a Modelfile is an iterative process. Test your model thoroughly and adjust the Modelfile as necessary to refine its performance and capabilities.


The Ollama Modelfile is a powerful tool for developers looking to harness the full potential of AI and machine learning in their projects. By understanding and utilizing the structured yet flexible framework it provides, developers can create, share, and deploy models with unprecedented efficiency. Whether you’re building a playful assistant or a sophisticated AI system, the Modelfile is your gateway to bringing your vision to life in the Ollama ecosystem.

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