LFCS Essential Commands Practice Question
Exhibit
Refer to the exhibit. $ ls -l /usr/local/bin/backup.sh -rwx------ 1 root root 1024 Jan 1 12:00 /usr/local/bin/backup.sh $ sudo -u backup /usr/local/bin/backup.sh sudo: unable to execute /usr/local/bin/backup.sh: Permission denied $ id backup uid=1003(backup) gid=1003(backup) groups=1003(backup)
The backup script fails to run as user 'backup' with sudo. What is the issue?
⚠ Common exam trap
Many candidates assume sudo bypasses all file permission checks, but in reality, sudo only bypasses the permission to run the command as another user—the kernel still enforces file execute permissions on the target script.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The script does not have execute permission for the 'backup' user.
For a script to be executed via sudo, the user (backup) must have execute permission on the script file. Even if sudo is configured to allow the user to run the script, the operating system enforces file permission checks at execution time. Without the execute bit set for the backup user (or for others, depending on the sudo runas context), the kernel will refuse to execve() the script, resulting in a 'Permission denied' error.
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 has a restrictive umask.
Why it's wrong here
Umask affects new files, not existing permissions.
- ✓
The script does not have execute permission for the 'backup' user.
Why this is correct
Only root has execute permission.
- ✗
The script is not owned by 'backup'.
Why it's wrong here
Ownership is not the issue; execute permission is missing.
- ✗
The 'backup' user is not in the sudoers file.
Why it's wrong here
sudo is working, but the script is not executable.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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