---
name: lcgenv
description: >-
  Use when selecting or debugging standalone CERN LCG software from CVMFS:
  choosing an LCG view and platform, sourcing its environment, checking package
  versions, or avoiding conflicts between LCG views and experiment releases.
---

# CERN LCG views

LCG views provide coherent builds of ROOT and the scientific Python stack under
`/cvmfs/sft.cern.ch/lcg/views`. Prefer a complete view when several packages
must be ABI-compatible; use `lcgenv` only when a site workflow specifically
requires selecting individual packages.

## Select and verify

1. Identify the operating-system, architecture, compiler, and build type of the
   host before choosing a platform directory.
2. Inspect the available releases and platforms rather than guessing a path.
3. Source exactly one matching view:

```bash
source /cvmfs/sft.cern.ch/lcg/views/LCG_<release>/<platform>/setup.sh
```

4. Verify the effective tools, not only environment variables:

```bash
command -v python root-config
python --version
root-config --version
python -c 'import ROOT; print(ROOT.gROOT.GetVersion())'
```

Use the exact release and platform required by the analysis or build. Do not
layer unrelated LCG views, virtual environments, or experiment releases unless
their documentation explicitly supports it: `PATH`, `PYTHONPATH`, and shared
libraries can otherwise come from incompatible builds.

If CVMFS is unavailable, use the project's supported container or package
environment instead of copying pieces of a view. Record the chosen LCG release
and platform in reproducibility metadata.