essay
easy
Understand
permissions-anatomy
2 points
Question 5. CSCD240-E1-A
Describe what r, w, x, and - mean and what each group of three symbols means.
Work the drill
Answer on paper or in a terminal before revealing the ideal answer.
Ideal answer
r=read, w=write, x=execute, - = that permission denied. Three triads: owner (first 3), group (next 3), other (last 3).
Misconception bank
Each row below is a plausible wrong answer, the thinking that produces it, and the remedy that corrects the misconception. These are the foundation of the multiple-choice framing and the targeted feedback a student receives after answering.
r=root, w=write, x=execute
Misconception. Mnemonic confusion — "r" misread as root/superuser.
Remedy. Correct mnemonic: Read/Write/eXecute. Explicit labeling exercise.
Three triads = owner, group, world
Misconception. "World" is imprecise but close; accept with minor deduction.
Remedy. "Other" is the canonical term; "world" is commonly used but less precise in grading.
Three triads describe owner for file, directory, and link
Misconception. Fundamental misreading — confuses triad structure with file-type axis.
Remedy. Reteach: triads are about WHO (user classes), not WHAT (file types).
Authority mappings
Hover any chip for the mapping justification; click to open the authority record.
DCWF roles:
IT-451 System Administrator
Course-artifact links
Lectures
- CSCD240-S26-L05. Permissions part 1: ls -l anatomy, rwx, file types
Lab questions
- CSCD240-S26-LAB3: Given 5 ls -l lines, identify file type, owner/group/other perms.
CTF challenges
- 02 Permissions: Three Circles of Trust
- 02 Permissions: Octal Arithmetic