If the group permissions are removed, then members of that group (who are not the owner) will lose their access to the file.
In Linux, permissions are checked as a "waterfall." Once the system finds a category that matches you, it applies those rules and stops checking.
Let's see an example:
Imagine your example.txt file has these permissions:
-rw- --- ---
- Owner (rw-): The owner can Read and Write.
- Group (---): The group has zero permissions.
- Others (---): Everyone else has zero permissions.
If you and I are in the same group, but I am the owner and you are just a group member:
- I can still read/write the file (because the system sees I am the owner).
- You will get a "Permission denied" error (because the system sees you are in the group, but the group permissions are empty).
The "Step-by-Step" Check
When you try to open a file, the Linux kernel asks:
- "Are you the Owner?"
- If Yes: Use the first set of permissions (Owner). Done.
- "If No, are you in the Group?"
- If Yes: Use the second set (Group). Done.
- Crucial: If the group permissions are
---, you get nothing, even if the "Others" permissions are higher!
- "If No to both, use 'Other' permissions."
Summary
If you remove group permissions:
- The Owner is unaffected.
- Group members (who aren't the owner) are locked out.
- Others are still restricted by the "Other" permission set.
In the next steps of this lab, you'll actually learn how to use the chmod command to add or remove these specific permissions yourself! Ready to try it?
