> ## Documentation Index
> Fetch the complete documentation index at: https://notes.kodekloud.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Modelfile Introduction
> This article explains Modelfiles and their use in customizing open-source models with Ollama.
In this lesson, you’ll discover what a Modelfile is and how to tailor open-source models using Ollama. We’ve already covered running models locally, explored Ollama’s commands and features, built AI applications, and switched from Ollama to OpenAI keys for production deployments.
## Recap
* Running models locally with Ollama
* Key commands and features
* Building AI-powered applications for production
***
## Use Case: Gromor’s Customized Model
Gromor, an investment and portfolio management firm, wants its AI assistant to interpret monetary values in Indian rupees. By creating a Modelfile, Gromor can instruct the base model to output “₹100” instead of “100” when dealing with rupees.
***
## Modelfile vs. Dockerfile
A Modelfile is to Ollama what a Dockerfile is to Docker.
Both files start from a base image and layer on custom instructions to produce a final artifact.
### Dockerfile Workflow
1. `FROM ubuntu:20.04`
2. `RUN apt-get update && apt-get install -y python3`
3. Other build steps…
### Modelfile Workflow
1. `FROM :`
2. `PARAMETER` declarations
3. `SYSTEM` and `MESSAGE` instructions
***
## Common Modelfile Fields
Below are the most frequently used instructions in a Modelfile:
### 1. FROM
Specifies the base model image to extend:
```dockerfile theme={null}
FROM facebook/opt-1.3b:latest
```
### 2. PARAMETER
Declare hyperparameters that control the model’s output:
| Parameter | Purpose | Example |
| ----------- | ---------------------------------------- | ----------------- |
| temperature | Creativity vs. precision (0–1) | `0.2` for factual |
| num\_ctx | Max tokens in context | `512` |
| top\_k | Restrict candidate tokens per generation | `50` |
```modelfile theme={null}
# Lower temperature yields more factual outputs
PARAMETER temperature 0.2
```
Setting `temperature` too high (e.g., ≥0.9) can produce overly creative or inconsistent responses.
### 3. SYSTEM
Define a high-level system message to steer the model’s role:
```modelfile theme={null}
SYSTEM "You are a financial assistant fluent in INR notation."
```
### 4. MESSAGE
Provide dialogue history to establish context:
```modelfile theme={null}
MESSAGE user "Where is Wayne Manor?"
MESSAGE assistant "Wayne Manor is in Gotham City, New Jersey."
```
***
## Next Steps
You now know how to build a Modelfile with `FROM`, `PARAMETER`, `SYSTEM`, and `MESSAGE` instructions.\
For a comprehensive list of Modelfile directives, see the [Ollama Modelfile documentation](https://github.com/ollama/ollama#modelfile).