How Linux Works (2nd Edition) [PDF]

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How Linux Works (2nd Edition) – Book

The number one cause of all shared library problems is the environment variable named LD_LIBRARY_PATH. Setting this variable to a colon-delimited set of directory names makes ld.so search the given directories before anything else when looking for a shared library. This is a cheap way to make programs work when you move a library around, if you don’t have the program’s source code and can’t use patchelf, or if you’re just too lazy to recompile the executables. Unfortunately, you get what you pay for.

Never set LD_LIBRARY_PATH in shell startup files or when compiling software. When the dynamic runtime linker encounters this variable, it must often search through the entire contents of each specified directory more times than you’d care to know. This causes a big performance hit, but more importantly, you can get conflicts and mismatched libraries because the runtime linker looks in these directories for every program.

If you must use LD_LIBRARY_PATH to run some crummy program for which you don’t have the source (or an application that you’d rather not compile, like Mozilla or some other beast), use a wrapper script. Let’s say your executable is /opt/crummy/bin/crummy.bin and needs some shared libraries in /opt/crummy/lib. Write a wrapper script called crummy.