A developer wants to test a single program against a private build of a library in ~/testlib, without changing anything system-wide or affecting other users. What is the appropriate mechanism?
LPIC-1 Exam 101-500, objective 102. Linux installation and package management medium
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The options
Not correct Add ~/testlib to /etc/ld.so.conf.d/ and run ldconfig
Wrong for the requirement. This works technically but is exactly the system-wide change the developer wanted to avoid, and it needs root.
Correct Set the LD_LIBRARY_PATH environment variable to ~/testlib for that program's invocation
Correct. LD_LIBRARY_PATH adds directories the dynamic linker searches ahead of the cached system paths, and because it is an environment variable its effect is limited to that process and its children.
Not correct Set the PATH environment variable to include ~/testlib
Wrong. PATH is searched by the shell for executables to run; the dynamic linker does not consult it when resolving shared libraries.
Not correct Run ldd with the library directory so it prefers the private build
Wrong. ldd only reports dependencies; it has no ability to change how future programs resolve libraries.
Why
LD_LIBRARY_PATH is a colon-separated list of directories the dynamic linker searches before the cache, which makes it the standard way to test or run software against non-system libraries per process. Because it can redirect a program to attacker-supplied libraries, the linker ignores it for set-user-ID and set-group-ID binaries, and leaving it set globally in a login profile is a well-known way to create confusing breakage.
Where this comes from
- Cited
- LPI exam objective 102.3
- What it says
- LD_LIBRARY_PATH and the locations of shared libraries.
Practise this
Reading one question is not practice. The trainer will draw a set from objective 102 and space the ones you get wrong.