Inode-based file systems (ext4) in Operating Systems - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What is the primary role of an inode in ext4 file systems?

In the ext4 file system, what does an inode mainly store?

A The actual content of the file

B Metadata about a file such as permissions, ownership, and file size

C The file name and directory path

D The backup copy of the file data

💡 Hint

Think about what information is needed to manage a file without storing its name or content.

An inode stores metadata about a file, including permissions, ownership, timestamps, and pointers to the file's data blocks. It does not store the file name or the actual content.

📋 Factual

intermediate

How does ext4 locate a file's data on disk?

Which structure in ext4 points to the actual data blocks of a file?

A The inode contains pointers to the data blocks

B The superblock contains pointers to the data blocks

C The directory entry contains pointers to the data blocks

D The journal contains pointers to the data blocks

💡 Hint

Consider where the file system stores the location of file content.

The inode holds pointers to the data blocks where the file's actual content is stored. Directory entries only map file names to inode numbers.

🔍 Analysis

advanced

Why does ext4 use indirect pointers in inodes?

Ext4 inodes have direct, single indirect, double indirect, and triple indirect pointers. Why are indirect pointers used?

A To allow files to be larger than what direct pointers alone can address

B To speed up file access by storing data in multiple places

C To store file names within the inode

D To keep a backup of file data in case of corruption

💡 Hint

Think about file size limits and how pointers can extend addressing capacity.

Direct pointers can only address a limited number of blocks. Indirect pointers add layers of referencing, allowing the file system to handle very large files by pointing to blocks that themselves contain pointers.

❓ Comparison

advanced

Difference between inode number and file name in ext4

Which statement correctly describes the relationship between inode numbers and file names in ext4?

A Inode numbers are only used for directories, not files

B Inode numbers store file names directly inside the inode structure

C File names and inode numbers are the same and interchangeable

D File names are stored in directory entries that map to inode numbers; inode numbers do not store file names

💡 Hint

Consider how the file system links names to metadata.

In ext4, directory entries hold file names and link them to inode numbers. The inode itself does not contain the file name but stores metadata and pointers to data.

❓ Reasoning

expert

What happens if an inode is deleted but directory entry remains?

In ext4, if an inode is deleted but the directory entry pointing to it is not removed, what is the likely outcome?

A The inode is automatically restored by the file system

B The file content remains accessible normally

C The directory entry points to invalid data, causing file access errors

D The file system merges the inode with another file's inode

💡 Hint

Think about what happens when metadata is missing but references remain.

If the inode is deleted but the directory entry still exists, the directory entry points to a non-existent inode. This causes errors when trying to access the file because the metadata and data pointers are missing.

Practice

1. What is the primary role of an inode in an ext4 file system?

easy

A. To store metadata about a file, such as permissions and size

B. To store the actual content of the file

C. To store the file name and directory path

D. To manage network connections for file sharing

Solution

1. Step 1: Understand what an inode stores

   An inode contains metadata like file size, ownership, permissions, and timestamps, but not the file content or name.

2. Step 2: Differentiate inode from file content and name

   The actual file content is stored in data blocks, and file names are stored in directory entries, separate from inodes.

3. Final Answer:

   To store metadata about a file, such as permissions and size -> Option A

4. Quick Check:

   Inode = File metadata [OK]

Hint: Inode holds file info, not content or name [OK]

Common Mistakes:

• Confusing inode with file content storage
• Thinking inode stores file names
• Assuming inode manages network features

2. Which of the following is the correct way to find the inode number of a file named example.txt in Linux?

easy

A. cat -i example.txt

B. find inode example.txt

C. inode example.txt

D. ls -i example.txt

Solution

1. Step 1: Recall Linux command to show inode

   The ls -i command lists files with their inode numbers.

2. Step 2: Verify other options

   cat shows file content, inode is not a standard command, and find inode is incorrect syntax.

3. Final Answer:

   ls -i example.txt -> Option D

4. Quick Check:

   ls -i shows inode [OK]

Hint: Use ls -i to see inode numbers quickly [OK]

Common Mistakes:

• Using cat instead of ls
• Assuming inode is a command
• Trying incorrect find syntax

3. Consider the following scenario: You create two hard links to the same file in ext4. What will be the inode number relationship between the original file and the two hard links?

medium

A. All three have different inode numbers

B. The original file and hard links share the same inode number

C. Only the original file has an inode number; hard links do not

D. Hard links have inode numbers, but the original file does not

Solution

1. Step 1: Understand hard links in ext4

   Hard links point to the same inode as the original file, meaning they share the same inode number.

2. Step 2: Confirm inode sharing

   Since hard links are just additional directory entries for the same inode, all share the same inode number.

3. Final Answer:

   The original file and hard links share the same inode number -> Option B

4. Quick Check:

   Hard links share inode [OK]

Hint: Hard links share inode number with original file [OK]

Common Mistakes:

• Thinking hard links have unique inodes
• Believing hard links lack inode numbers
• Confusing hard links with symbolic links

4. You run ls -i and see two files with the same inode number. What is the most likely explanation?

medium

A. They are hard links to the same file

B. They are symbolic links to different files

C. They are files with identical content but different inodes

D. It is a display error in the terminal

Solution

1. Step 1: Interpret same inode numbers in ls -i output

   Files with the same inode number are hard links pointing to the same file data.

2. Step 2: Rule out other options

   Symbolic links have different inodes, identical content files have different inodes, and terminal display errors are rare and unlikely.

3. Final Answer:

   They are hard links to the same file -> Option A

4. Quick Check:

   Same inode means hard links [OK]

Hint: Same inode number means hard links [OK]

Common Mistakes:

• Confusing symbolic links with hard links
• Assuming identical content means same inode
• Blaming terminal display errors

5. In ext4, if a file's inode is deleted but its data blocks remain, what is the likely consequence?

hard

A. The system automatically recovers the inode and file

B. The file content is still accessible via its filename

C. The file becomes inaccessible, causing potential data loss

D. The file is moved to a hidden backup directory

Solution

1. Step 1: Understand inode deletion impact

   Deleting an inode removes the metadata and reference to the file, making it inaccessible even if data blocks exist.

2. Step 2: Explain why data blocks alone are insufficient

   Without the inode, the system cannot locate or manage the file data, leading to potential data loss.

3. Final Answer:

   The file becomes inaccessible, causing potential data loss -> Option C

4. Quick Check:

   Deleted inode = inaccessible file [OK]

Hint: No inode means no access to file data [OK]

Common Mistakes:

• Assuming file remains accessible without inode
• Believing system auto-recovers deleted inodes
• Thinking file moves to backup automatically