Linux File Permissions quiz challenge | Linux File Permissions interview Questions and Answers multi choice

Linux Permissions Challenge - Octal & Symbolic

🔒 Linux File Permissions Challenge

Master the basics of `chmod` and `chown`. **Pass with 80% to proceed to the next difficulty level.**

Octal Basics: 0/10 (0%)

Symbolic & SUID: 0/10 (0%)

Chown & Advanced: 0/10 (0%)

Level 1: Octal Notation Fundamentals

1.1 What octal value represents the Read permission only?

A. 1 B. 4 C. 2

**Correct Answer: B. 4**. Read (r) is 4, Write (w) is 2, Execute (x) is 1.

1.2 What does the octal permission 755 represent?

A. Owner: rwx, Group: rw-, Others: r-- B. Owner: rwx, Group: rwx, Others: rwx C. Owner: rwx, Group: r-x, Others: r-x

**Correct Answer: C.** 7 (4+2+1) is rwx. 5 (4+1) is r-x.

1.3 To grant a file full read, write, and execute permissions to all users, what is the correct octal code?

A. 666 B. 700 C. 777

**Correct Answer: C. 777**. Full permissions (rwx = 7) for Owner (7), Group (7), and Others (7).

1.4 What is the command line syntax to set permissions to rwxr-x--- for a file named `script.sh`?

A. `chmod 750 script.sh` B. `chmod 750 script.sh` C. `chmod 760 script.sh`

**Correct Answer: B. `chmod 750 script.sh`**. Owner (rwx = 7), Group (r-x = 5), Others (--- = 0).

1.5 What octal value represents Read and Write permissions (`rw-`)?

A. 3 B. 5 C. 6

**Correct Answer: C. 6**. Read (4) + Write (2) = 6.

1.6 A file has permissions 440. What permissions does the Group have?

A. Read (r) B. Read (r) C. Read and Write (rw)

**Correct Answer: B. Read (r)**. The second digit '4' means Read only (r--).

1.7 Which command would make a file read-only for everyone?

A. `chmod 222 filename` B. `chmod 666 filename` C. `chmod 444 filename`

**Correct Answer: C. `chmod 444 filename`**. The octal 4 is Read permission (r--).

1.8 What is the octal code for Owner: rwx, Group: rw-, Others: r--?

A. 754 B. 764 C. 744

**Correct Answer: B. 764**. Owner=7 (rwx), Group=6 (rw-), Others=4 (r--).

1.9 Which octal value gives Write and Execute permissions only?

A. 5 B. 7 C. 3

**Correct Answer: C. 3**. Write (2) + Execute (1) = 3.

1.10 When setting permissions for a directory, what is the minimum necessary permission to use the `cd` command into it?

A. Read (4) B. Execute (1) C. Write (2)

**Correct Answer: B. Execute (1)**. For directories, execute (`x`) grants the ability to traverse/access.

**End of Octal Basics. Click "Next Level" to continue.**

Level 2: Symbolic Notation and Special Bits

2.1 What does the command `chmod u+x file.txt` do?

A. Adds write permission for all users. B. Removes execute permission for the owner. C. Adds execute permission for the file's owner.

**Correct Answer: C.** `u` (user/owner), `+` (add permission), `x` (execute).

2.2 Which symbolic command removes read and write permissions for others?

A. `chmod o-w file` B. `chmod o-rw file` C. `chmod a-rw file`

**Correct Answer: B.** `o` (others), `-` (remove), `rw` (read/write).

2.3 What does the SUID (Set User ID) special bit allow?

A. All files created in the directory inherit the directory's group ownership. B. The program executes with the permissions of the **file owner**, not the user running it. C. Users can only delete files they own within a shared directory.

**Correct Answer: B.** This is crucial for commands like `passwd` which run as root regardless of the actual user.

2.4 Which octal value is used to set the SUID bit?

A. 4000 B. 4000 (Prepended to regular permissions) C. 1000

**Correct Answer: B. 4000**. It's the leftmost digit. E.g., `chmod 4755 file`.

2.5 Which symbolic command sets execute permission for all three categories (owner, group, others)?

A. `chmod +x file` B. `chmod a=x file` C. `chmod a+x file`

**Correct Answer: C. `chmod a+x file`**. When the category is omitted (like in `chmod +x`), it defaults to *all* (`a`). `a=x` would remove all other permissions.

2.6 What does the letter `g` stand for in symbolic permission mode?

A. Global B. Group C. Guest

**Correct Answer: B. Group**. The symbolic notations are: `u` (user), `g` (group), `o` (others), `a` (all).

2.7 If a file shows permissions as `-rwsr-xr-x`, which special bit is set?

A. Sticky bit (t) B. SUID (s) C. SGID (s in the group field)

**Correct Answer: B. SUID (s)**. The `s` is in the owner's execute position. If it was lowercase, the underlying execute permission is also set.

2.8 What is the effect of the SGID (Set Group ID) bit on a directory?

A. Makes the directory read-only. B. New files/subdirectories created inside inherit the group ownership of the parent directory. C. The directory can only be accessed by the file owner.

**Correct Answer: B.** This is commonly used for shared directories so all users in a group can share content easily.

2.9 The octal code for SGID (Set Group ID) is:

A. 4000 B. 2000 C. 1000

**Correct Answer: B. 2000**. SUID=4000, SGID=2000, Sticky=1000.

2.10 If a file's permissions are initially rwxr-xr--, what will be the result of `chmod g+w,o-r file`?

A. `rwxrwx---` B. `rwxrwxr--` C. `rwxrwx---`

**Correct Answer: C. `rwxrwx---`**. Group permissions become rwx (r-x + w = rwx). Others lose read (r-- - r = ---).

**End of Symbolic Level. Click "Next Level" to continue.**

Level 3: Ownership and Advanced Concepts

3.1 Which command is used to change the owner of a file?

A. `chmod` B. `chown` C. `chgrp`

**Correct Answer: B. `chown`** (Change Owner).

3.2 What is the command to change the owner to `alice` and the group to `devs` for `project.zip`?

A. `chown alice:project.zip devs` B. `chown alice:devs project.zip` C. `chown -R alice devs project.zip`

**Correct Answer: B.** The syntax is `chown user:group file`.

3.3 What does the sticky bit (represented by `t` in the others' execute field) do on a world-writable directory like `/tmp`?

A. Prevents the directory from being renamed. B. Prevents users from deleting or renaming files in the directory that they do not own. C. Forces new files to inherit the group owner of the creating user.

**Correct Answer: B.** The sticky bit is essential for multi-user directories to prevent file anarchy.

3.4 Which command changes the group ownership of a file without affecting the owner?

A. `chown` B. `chperm` C. `chgrp`

**Correct Answer: C. `chgrp`** (Change Group). You can also use `chown :newgroup file.txt`.

3.5 What is the difference between `chown user file` and `chown user.group file`?

A. They are identical. B. The second form changes both the owner and the group simultaneously. C. The second form changes the owner to 'user' and the group to the owner's primary group.

**Correct Answer: B.** The colon (`:`) or dot (`.`) separates the user and the group in `chown`.

3.6 What does the Umask setting determine?

A. The permissions of the root user. B. The maximum allowed permissions for executable files. C. The default permissions newly created files and directories will **NOT** have.

**Correct Answer: C.** Umask subtracts (or masks out) permissions from the maximum default permissions (666 for files, 777 for directories).

3.7 What will be the permissions of a new file if the umask is 0022? (Max file perm is 666)

A. 755 (rwxr-xr-x) B. 644 (rw-r--r--) C. 644 (rw-r--r--)

**Correct Answer: C. 644**. File max is 666. 666 - 022 = 644.

3.8 To recursively change the permissions of a directory and all its contents, what flag is used with `chmod`?

A. `-f` B. `-R` C. `-L`

**Correct Answer: B. `-R`** (Recursive). This flag is also used with `chown`, `chgrp`, `cp`, and `rm`.

3.9 A file shows permissions as `-rw-r--r--`. If the Sticky bit is set, how would the long listing (`ls -l`) change?

A. It would show `t` instead of `-` in the owner's execute position. B. It would show `T` instead of `-` in the others' execute position. C. The permissions would remain the same, as the sticky bit only affects directories.

**Correct Answer: B.** Since the others' execute bit is NOT set, the sticky bit shows as a capital **T** in that position (`-rw-r--r-T`). If execute was set, it would be a lowercase `t`.

3.10 In Linux, which entity determines if you can delete a file?

A. The permissions on the file itself. B. The write (`w`) and execute (`x`) permissions on the **parent directory**. C. The file must have both read (`r`) and write (`w`) permissions.

**Correct Answer: B.** Deleting a file requires modifying the directory's contents, thus requiring write/execute permission on the *directory*, not the file.

**Permissions Mastered! Click "Finish Quiz" to see your final summary.**

Final Quiz Summary 📋

Related Topics & Tags

Linux Permissions chmod chown Octal Symbolic SUID SGID StickyBit SysAdmin Security Umask FileSystem Commands SecurityHardening

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