BeginnerPhone
2 min
Linux File Permissions Basics
LinuxSystem AdministrationSecurity
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Interview Question
Explain the meaning of rwx for user, group, and others, and how chmod/chown modify permissions.
Key Points to Cover
- r=read, w=write, x=execute across user/group/others
- `chmod` changes mode (symbolic or octal), `chown` changes owner/group
- Common octal: 644 files, 755 dirs/binaries
Evaluation Rubric
Correctly explains rwx and U/G/O40% weight
Describes chmod usage30% weight
Describes chown usage30% weight
Hints
- 💡Remember directories need x to enter.
Common Pitfalls to Avoid
- ⚠️Confusing the purpose of `chmod` (permissions) with `chown` (ownership).
- ⚠️Not clearly explaining the meaning of the 'execute' permission (`x`) when applied to directories (i.e., allowing traversal/access).
- ⚠️Failing to articulate how octal values (4 for r, 2 for w, 1 for x) are derived and summed for each permission category.
- ⚠️Omitting common octal permission examples like `644` for files and `755` for directories or executables.
- ⚠️Neglecting to mention the symbolic method of `chmod` (e.g., `u+rwx`) in addition to the octal method.
Potential Follow-up Questions
- ❓What is umask?
- ❓How do setuid/setgid/sticky bits work?
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