lcgenv

name	lcgenv
description	Use when setting up standalone LCG (CERN SFT) software packages via lcgenv or views: listing available LCG releases and platforms, configuring individual packages from a specific LCG release, setting up an entire LCG release at once with views, or combining LCG packages with other ATLAS tools like ROOT or rucio.

lcgenv and views

Overview

lcgenv and views are two mechanisms for setting up software from the LCG (CERN SFT) stack distributed via CVMFS. lcgenv provides fine-grained control, allowing individual packages and their dependencies to be configured from a specific LCG release. views provides a coarse-grained alternative that sets up an entire LCG release at once. Both are accessed via lsetup after running setupATLAS.

When to Use

• Setting up a specific Python, HEP, or math library from an LCG release without loading a full ATLAS release
• Listing available LCG releases, platforms, and packages
• Setting up multiple LCG packages with compatible versions from the same release
• Quickly activating an entire LCG release environment via views
• Combining LCG packages with standalone ATLAS tools (ROOT, rucio, etc.)

Key Concepts

LCG release: A coordinated software stack (e.g., LCG_104) containing versioned builds of ROOT, Python, Boost, and hundreds of other packages. Built for specific platforms and distributed via /cvmfs/sft.cern.ch.

Platform string: <arch>-<os>-<compiler>-<mode>, e.g., x86_64-el9-gcc13-opt. Determines which binary build to use.

lcgenv vs views:

Aspect	lcgenv	views
Granularity	Individual packages	Entire LCG release
Speed	Slower (resolves dependencies)	Faster (single setup)
Flexibility	Pick only what you need	All-or-nothing
Use case	Minimal environment, mixing	Full LCG stack needed

Canonical Patterns

List available LCG releases

lsetup "lcgenv"

List platforms for a release

lsetup "lcgenv -p LCG_104"

List packages available in a release

lsetup "lcgenv -p LCG_104 x86_64-el9-gcc13-opt"

Set up a single package

lsetup "lcgenv -p LCG_104 x86_64-el9-gcc13-opt pyanalysis"

This configures the package and all its dependencies in the current shell.

Set up multiple packages

Each package must be a separate quoted lcgenv invocation:

lsetup \
  "lcgenv -p LCG_104 x86_64-el9-gcc13-opt pygraphics" \
  "lcgenv -p LCG_104 x86_64-el9-gcc13-opt pyanalysis"

Combine with other lsetup tools

lsetup \
  "lcgenv -p LCG_104 x86_64-el9-gcc13-opt pyanalysis" \
  "root 6.32" \
  rucio

List available LCG views releases

lsetup "views"

Set up a full LCG release with views

lsetup "views LCG_104 x86_64-el9-gcc13-opt"

This activates the entire software stack (ROOT, Python, Boost, etc.) from the specified release in one command.

Check which package version is in a release

lsetup "lcgenv -p LCG_104 x86_64-el9-gcc13-opt" | grep -i boost

The output lists all available packages with their versions; grep to find a specific one.

Common packages available via lcgenv

Package	Description
pyanalysis	Python analysis stack (numpy, etc.)
pygraphics	Plotting libraries (matplotlib, etc.)
Boost	Boost C++ libraries
eigen	Eigen linear algebra library
hdf5	HDF5 data format library
fftw	Fast Fourier Transform library

Gotchas

• -p flag required for lcgenv: The release must be specified with -p (e.g., lcgenv -p LCG_104), not as a positional argument.
• Quoting is mandatory: lsetup arguments with spaces must be quoted — lsetup "lcgenv -p LCG_104 x86_64-el9-gcc13-opt pkg", not lsetup lcgenv -p LCG_104 ....
• views is all-or-nothing: Unlike lcgenv, views does not support selecting individual packages — it loads everything from the release.
• CVMFS access required: Both tools read from /cvmfs/sft.cern.ch. Ensure CVMFS is mounted and accessible.
• Platform must match the host: Using a platform string that does not match the running OS (e.g., slc6 on an EL9 host) produces broken environments. Check with cat /etc/os-release if unsure.
• Do not mix lcgenv and views in the same shell: Setting up a views release and then overlaying lcgenv packages from a different release can cause library conflicts.
• Older release names: Historical releases may use slc6 or centos7 in platform strings; current platforms use el9.

Interop

• setupATLAS: lsetup must be available before using lcgenv or views. Run setupATLAS first. See the setupatlas skill.
• ROOT: lsetup "root 6.32" sets up ROOT independently. Use lcgenv only when a specific LCG-bundled ROOT version is needed.
• asetup: Full ATLAS releases already include LCG packages. Do not layer lcgenv on top of an asetup environment — use one or the other.
• scikit-hep: lsetup scikit provides the scikit-hep ecosystem independently of LCG. Use lcgenv when a specific LCG-coordinated version is required.

Docs

• lcgenv: https://twiki.atlas-canada.ca/bin/view/AtlasCanada/Lcgenv
• views: Self-documenting via lsetup "views" (lists releases and platforms)
• LCG releases: https://lcginfo.cern.ch