Checkpoint & revision
Checkpoint and permission revision
Explain the result and keep a compact operating checklist.
Linux
Predict before you try
If a file is readable but its parent directory cannot be traversed, will the intended user be able to open it?
Try it: Apply the model to a new example →On this page
Demonstrate what you understood
Complete the lab before marking this checkpoint complete. In your notes, answer these prompts using your actual observations:
- Which identity attempted the read, and how did you establish it?
- Why could a readable file become inaccessible without changing its mode?
- Which exact repair restored access? Why was a recursive permission change unnecessary?
- What did your verification establish, and what did it leave untested?
- How did you confirm cleanup?
Completion is self-reported. The workspace cannot inspect your VM or verify terminal output.
Compare your reasoning
The changed object was the parent directory. Removing its owner search permission prevented path traversal in the specified regular-user setup. Restoring that bit allowed the same user to repeat the original read. This does not prove that another service account can read the file, that all security controls permit access, or that a real application deployment is healthy.
If your evidence differs, explain the difference rather than replacing it with this expected reasoning.
Apply the model to a new example
Try these without commands first, then compare the reasoning:
| Prompt | Answer and reason |
|---|---|
Read -rw-r----- numerically | 640: owner read/write, group read, others none |
A directory is 740; can a group member open a known child? | The group has r-- but no search bit, so ordinary path lookup through it fails |
A program requests file mode 666 under mask 027 | Expected ordinary mode is 640; the mask removes group write and all other bits |
Does umask 000 change an existing private file? | No; creation defaults and existing file modes are different |
| Does a second hard-link name create a backup? | No; both names refer to the same file data |
These answers assume ordinary mode checks without overriding ACLs or privileges. If you cannot explain one row, revisit the relevant filesystem or permissions worked example before starting process management. Being able to predict a new case is stronger than remembering the lab's one repair command.
Handy revision
| Question | First inspection |
|---|---|
| Where am I? | pwd |
| Who am I? | id |
| Who owns this directory? | ls -ld with the actual path |
| What can the owner do? | Read the first rwx permission group |
What does directory x mean? | Search entries by name |
| Did the repair work? | Repeat the original operation as the same user |
| Is this production evidence? | Only if the actual target environment and operation were tested |
Carry the habit forward
Continue with processes, services, and logs. Keep separating observation from explanation: a command that succeeds is useful evidence only when you can state what it tested.
Apply this evidence to your MicroBank readiness project. Record the actual permission diagnosis and repair as a learning entry, with environment details and limitations.
Apply this to MicroBank
Add the diagnosed path, observed identity, one-bit repair, and same-user verification to the MicroBank readiness record. Then write the additional check needed for a future runtime identity. This keeps the original permission outcome concrete while distinguishing your course fixture from an application deployment.
Keep this observation in the MicroBank readiness project.
Sources
Revision organized for LearnWithSK from the preceding bites and lab. Underlying reference: GNU permission modes↗.
Prove what you learned
Inspect the result
Compare intended-user access before and after the smallest scoped repair; retain the resulting modes.
Explain it in your own words
Explain why your observation supports the stated outcome, and name one thing it does not prove.
Try a small variation
Change one parent-directory permission in the disposable fixture instead of changing the file mode.
Your evidence should show
- Record the context/revision or label the work as a paper or prepared fixture.
- Compare the prediction with the actual result from “Apply the model to a new example”.
- Compare intended-user access before and after the smallest scoped repair; retain the resulting modes.
- Explain the transfer challenge and retain the same verification question.
Hint
Inspect the effective user and each parent directory, not only the file.
Answer guide: compare after predicting
No. Directory search permission and the file permission are separate checks. Verify as the intended identity.
Compare this with your actual observation. A paper answer is useful reasoning practice; record execution separately.
Recall how a path is resolved from the current directory. Revisit the previous lesson.
Save the prediction, result and explanation ↓Your notes and evidence
Record observations, questions, or links to your work. Keep credentials out of your notes.
Back up or restore this path
Progress and notes stay in this browser. A backup contains only this learning path.