TL;DR: lightgbm needs the OpenMP runtime library and your Linux box does not have it. Install the libgomp system package and the import works.

## The error
```text
OSError: libgomp.so.1: cannot open shared object file: No such file or directory
```

## Fix it
1. Install the OpenMP runtime. On Debian/Ubuntu:
   ```
   sudo apt install libgomp1
   ```
   On RHEL/Fedora: `sudo dnf install libgomp`. Expected: package installs.
2. Verify the library resolves:
   ```
   ldconfig -p | grep libgomp
   ```
   Expected: a line showing libgomp.so.1.
3. Retry:
   ```
   python -c "import lightgbm; print(lightgbm.__version__)"
   ```
   Expected: prints the version.
4. Alternative: install lightgbm from conda-forge, which bundles the runtime:
   ```
   conda install -c conda-forge lightgbm
   ```

## When this applies
Use this when `import lightgbm` on Linux raises the libgomp.so.1 error.

## When it does not apply
On macOS the equivalent missing library is libomp.dylib (brew install libomp). If a different .so is missing, install that library instead.

## Compatibility
Linux, lightgbm pip wheels that link the system OpenMP.

## Root cause
lightgbm's compiled core links against libgomp for OpenMP parallelism. Minimal docker images and stripped servers often lack the libgomp runtime package, so the dynamic loader fails at import.

## Edge cases
In docker, add the package to the Dockerfile so rebuilds do not regress. On clusters without sudo, the conda-forge build is the way out since it carries its own runtime.