build-and-dependency

name	build-and-dependency
description	Build and dependency management for NeMo-RL. Covers Docker image building and running, uv usage, venv setup, and adding dependencies.
when_to_use	Setting up a dev environment; building or running the Docker container; adding or removing a dependency; uv errors; 'how do I install', 'ModuleNotFoundError', 'build the image', 'run in Docker', 'uv sync fails'.

Build and Dependency Guide

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Docker Images

Build the release image (includes all dependencies and pre-fetched venvs):

# Build from local source
docker buildx build -f docker/Dockerfile --tag nemo-rl:latest .

# Build from a specific git ref (no local clone needed)
docker buildx build -f docker/Dockerfile \
    --build-arg NRL_GIT_REF=main \
    --tag nemo-rl:latest \
    https://github.com/NVIDIA-NeMo/RL.git

Skip optional backends to reduce build time:

# Skip vLLM and SGLang
docker buildx build -f docker/Dockerfile \
    --build-arg SKIP_VLLM_BUILD=1 \
    --build-arg SKIP_SGLANG_BUILD=1 \
    --tag nemo-rl:latest .

See @docs/docker.md for full options.

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Always Use uv

Never use pip install directly — always go through uv.

# Run a script
uv run examples/run_grpo.py

# Run tests
uv run --group test bash tests/run_unit.sh

# Install all deps from lockfile
uv sync --locked

Exception: Dockerfile.ngc_pytorch is exempt from this rule.

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Adding Dependencies

# Add a runtime dependency
uv add <package>

# Add an optional dependency
uv add --optional --extra <group> <package>

# Regenerate the lockfile after changes
uv lock

Commit both pyproject.toml and uv.lock together:

git add pyproject.toml uv.lock
git commit -s -m "build: add <package> dependency"

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Common Pitfalls

Problem	Cause	Fix
uv sync --locked fails	Dependency conflict or stale lockfile	Re-run uv lock and commit updated lock
ModuleNotFoundError after pip install	pip installed outside uv-managed venv	Use uv add + uv sync, never bare pip install
Docker build fails at vLLM	vLLM build time overhead	Pass --build-arg SKIP_VLLM_BUILD=1