Quick Answer
The answer is LD_LIBRARY_PATH, the environment variable that must be checked or set when a custom application fails to run after a system update due to a shared library residing in a non-standard path. This variable instructs the dynamic linker, ld.so, to search specified directories for shared libraries before falling back to the default system paths like /usr/lib or /lib, making it essential for resolving runtime linking errors when libraries are installed outside the standard hierarchy. On the CompTIA Linux+ XK0-005 exam, this scenario tests your understanding of the dynamic linker’s search order and how environment variables override default behavior—a common trap is confusing LD_LIBRARY_PATH with LD_PRELOAD, which preloads specific libraries rather than adding search directories. Remember the memory tip: “Library Path, not Preload” to keep the distinction clear.
This XK0-005 practice question tests your understanding of troubleshooting. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
After a system update, a custom application no longer runs due to a shared library error. The library exists on the system but is in a non-standard path. Which environment variable should be checked or set to resolve this?
LD_PRELOAD
Why wrong: LD_PRELOAD forces loading of specific libraries before all others, not for general library search.
PATH
Why wrong: PATH is for executables, not libraries.
LD_LIBRARY_PATH
This environment variable tells the dynamic linker where to find libraries.
LD_RUN_PATH
Why wrong: LD_RUN_PATH is used at link time to embed a search path, not at runtime.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
LD_LIBRARY_PATH
Option C is correct because the LD_LIBRARY_PATH environment variable tells the dynamic linker (ld.so) where to search for shared libraries before the standard system paths. When a custom application fails with a shared library error after an update, and the library exists in a non-standard path, setting LD_LIBRARY_PATH to include that path resolves the issue by allowing the linker to find the library at runtime.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
LD_PRELOAD
Why it's wrong here
LD_PRELOAD forces loading of specific libraries before all others, not for general library search.
PATH
Why it's wrong here
PATH is for executables, not libraries.
LD_LIBRARY_PATH
Why this is correct
This environment variable tells the dynamic linker where to find libraries.
Related concept
Read the scenario before looking for a memorised answer.
LD_RUN_PATH
Why it's wrong here
LD_RUN_PATH is used at link time to embed a search path, not at runtime.
Common exam traps
CompTIA often tests the distinction between LD_LIBRARY_PATH (runtime library search path) and LD_RUN_PATH (link-time RPATH embedding), causing candidates to confuse the two when the question explicitly mentions a runtime error after an update.
Detailed technical explanation
The dynamic linker (ld-linux.so) uses a specific search order: first, it checks the RPATH embedded in the binary (set via -rpath at link time), then LD_LIBRARY_PATH, then the system default paths (/lib, /usr/lib), and finally the RUNPATH. Setting LD_LIBRARY_PATH overrides the RPATH for the current session, making it a quick fix for runtime library resolution without recompiling the application. A subtle behavior is that setuid and setgid binaries ignore LD_LIBRARY_PATH for security reasons, requiring alternative methods like modifying /etc/ld.so.conf or using patchelf.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Troubleshooting — study guide chapter
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FAQ
Troubleshooting — This question tests Troubleshooting — Read the scenario before looking for a memorised answer..
The correct answer is: LD_LIBRARY_PATH — Option C is correct because the LD_LIBRARY_PATH environment variable tells the dynamic linker (ld.so) where to search for shared libraries before the standard system paths. When a custom application fails with a shared library error after an update, and the library exists in a non-standard path, setting LD_LIBRARY_PATH to include that path resolves the issue by allowing the linker to find the library at runtime.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
This XK0-005 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the XK0-005 exam.
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