LPIC-1 Shells, Scripting and Data Management Practice Question
This LPIC-1 practice question tests your understanding of shells, scripting and data management. 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.
A junior system administrator, Sarah, has written a shell script to automate a backup process on a Linux server. The script is located at /home/sarah/backup.sh and has execute permissions. The script contains the line 'mybackup /home/data'. The 'mybackup' command is installed in /usr/local/bin and works correctly when Sarah runs it from her interactive shell. However, when she runs the script using './backup.sh', it fails with the error 'line 5: mybackup: command not found'. Sarah has verified that /usr/local/bin is in her PATH by executing 'echo $PATH' in an interactive session. Which of the following is the most likely cause of this issue?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The script is running in a non-interactive shell that does not source Sarah's .bashrc file, so /usr/local/bin is not in the PATH.
Option B is correct. When a script runs, it starts a non-interactive shell that does not source the user's .bashrc or .profile, so custom PATH additions are not inherited. Option A would cause 'Permission denied'. Option C: aliases are not expanded in non-interactive shells, but the command is a real executable. Option D: the shebang line determines the interpreter; if /bin/sh is used, it may still have the same PATH issue, but the most direct cause is missing PATH.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
The script uses a different shell interpreter (e.g., /bin/sh instead of /bin/bash) that does not support the command.
Why it's wrong here
This would affect behavior but the primary issue is the PATH not including /usr/local/bin.
✓
The script is running in a non-interactive shell that does not source Sarah's .bashrc file, so /usr/local/bin is not in the PATH.
Why this is correct
Non-interactive shells do not source .bashrc, so custom PATH is missing.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
The 'mybackup' command is a shell alias, not a real executable.
Why it's wrong here
Aliases are not expanded in non-interactive shells, but the error is about the command not being found, not alias expansion.
✗
The script does not have the executable bit set.
Why it's wrong here
This would cause 'Permission denied', not 'command not found'.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Trap categories for this question
Command / output trap
Aliases are not expanded in non-interactive shells, but the error is about the command not being found, not alias expansion.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
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
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related LPIC-1 NAT questions on configuration and troubleshooting.
Shells, Scripting and Data Management — This question tests Shells, Scripting and Data Management — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The script is running in a non-interactive shell that does not source Sarah's .bashrc file, so /usr/local/bin is not in the PATH. — Option B is correct. When a script runs, it starts a non-interactive shell that does not source the user's .bashrc or .profile, so custom PATH additions are not inherited. Option A would cause 'Permission denied'. Option C: aliases are not expanded in non-interactive shells, but the command is a real executable. Option D: the shebang line determines the interpreter; if /bin/sh is used, it may still have the same PATH issue, but the most direct cause is missing PATH.
What should I do if I get this LPIC-1 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related LPIC-1 NAT questions on configuration and troubleshooting.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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