LPIC-1 GNU and Unix Commands Practice Question
Which THREE of the following are valid symbolic mode expressions for the chmod command?
⚠ Common exam trap
Candidates often confuse numeric (octal) modes with symbolic modes, or assume that any single-letter class like 'c' is valid, when only u, g, o, and a are recognized by the chmod command.
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
✓
u+x
'u+x' is a valid symbolic mode expression for chmod, where 'u' stands for the user (owner), '+' adds a permission, and 'x' is the execute permission. This syntax follows the POSIX standard for symbolic modes, allowing precise modification of file permissions without specifying an absolute octal value.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
u+x
Why this is correct
Adds execute permission for the user.
- ✗
755
Why it's wrong here
755 is numeric mode, not symbolic.
- ✓
a+rwx
Why this is correct
Adds read, write, execute for all categories.
- ✗
c+r
Why it's wrong here
'c' is not a valid category (u, g, o, a are valid).
- ✓
g-w
Why this is correct
Removes write permission for the group.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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