# Using uv in Docker

## Running in Docker

A Docker image is published with a built version of uv available. To run a uv command in a
container:

```console
$ docker run ghcr.io/astral-sh/uv --help
```

## Installing uv

uv can be installed by copying from the official Docker image:

```dockerfile title="Dockerfile"
FROM python:3.12-slim-bookworm
COPY --from=ghcr.io/astral-sh/uv:latest /uv /bin/uv
```

Or, with the installer:

```dockerfile title="Dockerfile"
FROM python:3.12-slim-bookworm

# The installer requires curl (and certificates) to download the release archive
RUN apt-get update && apt-get install -y --no-install-recommends curl ca-certificates

# Download the latest installer
ADD https://astral.sh/uv/install.sh /uv-installer.sh

# Run the installer then remove it
RUN sh /uv-installer.sh && rm /uv-installer.sh

# Ensure the installed binary is on the `PATH`
ENV PATH="/root/.cargo/bin/:$PATH"
```

Note this requires `curl` to be available.

In either case, it is best practice to pin to a specific uv version, e.g., with:

```dockerfile
COPY --from=ghcr.io/astral-sh/uv:0.3.3 /uv /bin/uv
```

Or, with the installer:

```dockerfile
ADD https://astral.sh/uv/0.3.3/install.sh /uv-installer.sh
```

## Installing a project

If you're using uv to manage your project, you can copy it into the image and install it:

```dockerfile title="Dockerfile"
# Copy the project into the image
ADD . /app
WORKDIR /app

# Sync the project into a new environment, using the frozen lockfile
RUN uv sync --frozen
```

Once the project is installed, you can either _activate_ the virtual environment:

```dockerfile title="Dockerfile"
# Use the virtual environment automatically
ENV VIRTUAL_ENV=/app/.venv
# Place executables in the environment at the front of the path
ENV PATH="/app/.venv/bin:$PATH"
```

Or, you can use `uv run` to run commands in the environment:

```dockerfile title="Dockerfile"
RUN uv run some_script.py
```

And, to start your application by default:

```dockerfile title="Dockerfile"
# Presuming there is a `my_app` command provided by the project
CMD ["uv", "run", "my_app"]
```

## Using installed tools

To use installed tools, ensure the [tool bin directory](../../concepts/tools.md#the-bin-directory)
is on the path:

```dockerfile title="Dockerfile"
ENV PATH=/root/.local/bin:$PATH
RUN uv tool install cowsay
```

```console
$ docker run -it $(docker build -q .) /bin/bash -c "cowsay -t hello"
  _____
| hello |
  =====
     \
      \
        ^__^
        (oo)\_______
        (__)\       )\/\
            ||----w |
            ||     ||
```

To determine the tool bin directory, run `uv tool dir --bin` in the container.

## Using the pip interface

### Installing a package

The system Python environment is safe to use this context, since a container is already isolated.
The `--system` flag can be used to install in the system environment:

```dockerfile title="Dockerfile"
RUN uv pip install --system ruff
```

To use the system Python environment by default, set the `UV_SYSTEM_PYTHON` variable:

```dockerfile title="Dockerfile"
ENV UV_SYSTEM_PYTHON=1
```

Alternatively, a virtual environment can be created and activated:

```dockerfile title="Dockerfile"
RUN uv venv /opt/venv
# Use the virtual environment automatically
ENV VIRTUAL_ENV=/opt/venv
# Place entry points in the environment at the front of the path
ENV PATH="/opt/venv/bin:$PATH"
```

When using a virtual environment, the `--system` flag should be omitted from uv invocations:

```dockerfile title="Dockerfile"
RUN uv pip install ruff
```

### Installing requirements

To install requirements files, copy them into the container:

```dockerfile title="Dockerfile"
COPY requirements.txt .
RUN uv pip install -r requirements.txt
```

### Installing a project

When installing a project alongside requirements, it is prudent to separate copying the requirements
from the rest of the source code. This allows the dependencies of the project (which do not change
often) to be cached separately from the project itself (which changes very frequently).

```dockerfile title="Dockerfile"
COPY pyproject.toml .
RUN uv pip install -r pyproject.toml
COPY . .
RUN uv pip install -e .
```

## Optimizations

### Using uv temporarily

If uv isn't needed in the final image, the binary can be mounted in each invocation:

```dockerfile title="Dockerfile"
RUN --mount=from=uv,source=/uv,target=/bin/uv \
    uv pip install --system ruff
```

### Compiling bytecode

Compiling Python source files to bytecode is typically desirable for production images as it tends
to improve startup time (at the cost of increased installation time).

To enable bytecode compilation, use the `--compile-bytecode` flag:

```dockerfile title="Dockerfile"
RUN uv sync --compile-bytecode
```

Alternatively, you can set the `UV_COMPILE_BYTECODE` environment variable to ensure that all
commands within the Dockerfile compile bytecode:

```dockerfile title="Dockerfile"
ENV UV_COMPILE_BYTECODE=1
```

### Caching

A [cache mount](https://docs.docker.com/build/guide/mounts/#add-a-cache-mount) can be used to
improve performance across builds:

```dockerfile title="Dockerfile"
RUN --mount=type=cache,target=/root/.cache/uv \
 ./uv pip install -r requirements.txt -->
```

Note the cache directory's location can be determined with the `uv cache dir` command.
Alternatively, the cache can be set to a constant location:

```dockerfile title="Dockerfile"
ENV UV_CACHE_DIR=/opt/uv-cache/
```

If not mounting the cache, image size can be reduced with `--no-cache` flag.

### Intermediate layers

If you're using uv to manage your project, you can improve build times by moving your transitive
dependency installation into its own layer via the `--no-install` options.

`uv sync --no-install-project` will install the dependencies of the project but not the project
itself. Since the project changes frequently, but its dependencies are generally static, this can be
a big time saver.

```dockerfile title="Dockerfile"
# Install uv
FROM python:3.12-slim
COPY --from=ghcr.io/astral-sh/uv:latest /uv /bin/uv

# Copy the lockfile and `pyproject.toml` into the image
ADD uv.lock /app/uv.lock
ADD pyproject.toml /app/pyproject.toml

# Install dependencies
WORKDIR /app
RUN uv sync --frozen --no-install-project

# Copy the project into the image
ADD . /app

# Sync the project
RUN uv sync --frozen
```

Note that the `pyproject.toml` is required to identify the project root and name, but the project
_contents_ are not copied into the image until the final `uv sync` command.

!!! tip

    If you're using a [workspace](../../concepts/workspaces.md), then use the
    `--no-install-workspace` flag which excludes the project _and_ any workspace members.

    If you want to remove specific packages from the sync, use `--no-install-package <name>`.