ln (hard and symbolic links) in Linux CLI - Commands & Configuration

Introduction

Sometimes you want to have multiple names or shortcuts for the same file without copying it. The ln command creates links that point to the original file, saving space and making file management easier.

When you want two filenames to refer to the exact same file data on disk without duplicating it.

When you want a shortcut to a file in another directory that updates if the original file changes.

When you want to organize files in different folders but keep them linked to a single source.

When you want to save disk space by avoiding duplicate copies of large files.

When you want to create a backup reference to a file that stays updated automatically.

Commands

Create a simple text file named original.txt with the content 'Hello World'. This file will be used to demonstrate links.

Terminal

echo "Hello World" > original.txt

Expected Output

No output (command runs silently)

Create a hard link named hardlink.txt pointing to original.txt. Both files share the same data on disk.

Terminal

ln original.txt hardlink.txt

Expected Output

No output (command runs silently)

Create a symbolic (soft) link named symlink.txt that points to original.txt. This is like a shortcut to the file.

Terminal

ln -s original.txt symlink.txt

Expected Output

No output (command runs silently)

→

-s - Create a symbolic link instead of a hard link

List the files with inode numbers and details to show how hardlink.txt shares inode with original.txt, but symlink.txt has a different inode.

Terminal

ls -li original.txt hardlink.txt symlink.txt

Expected Output

123456 -rw-r--r-- 2 user user 12 Jun 10 12:00 original.txt

123456 -rw-r--r-- 2 user user 12 Jun 10 12:00 hardlink.txt

123457 lrwxrwxrwx 1 user user 12 Jun 10 12:00 symlink.txt -> original.txt

→

-l - Show detailed file information

→

-i - Show inode number

Change the content of hardlink.txt. Since it is a hard link, original.txt content changes too.

Terminal

echo "New content" > hardlink.txt

Expected Output

No output (command runs silently)

Display the content of original.txt to confirm it changed after editing hardlink.txt.

Terminal

cat original.txt

Expected Output

New content

Remove the original.txt file. The hard link still keeps the data accessible.

Terminal

rm original.txt

Expected Output

No output (command runs silently)

Show that hardlink.txt still contains the data even after original.txt was deleted.

Terminal

cat hardlink.txt

Expected Output

New content

Try to read symlink.txt after original.txt is deleted. It will fail because the symbolic link points to a missing file.

Terminal

cat symlink.txt

Expected Output

cat: symlink.txt: No such file or directory

Key Concept

If you remember nothing else from this pattern, remember: hard links share the same file data and inode, while symbolic links are shortcuts that can break if the original file is removed.

Common Mistakes

Trying to create a hard link to a directory.

Hard links to directories are not allowed because they can break the file system structure.

Use symbolic links (-s) when linking directories.

Deleting the original file and expecting the symbolic link to still work.

Symbolic links point to the file name, so if the original file is deleted, the link breaks.

Keep the original file or use hard links if you want the data to persist.

Confusing hard links and symbolic links and their behavior.

Hard links share the same inode and data, symbolic links are separate files pointing to the original path.

Understand the difference and choose the right link type for your need.

Summary

Use ln to create hard links that share the same file data and inode.

Use ln -s to create symbolic links that act as shortcuts to files or directories.

Hard links keep data accessible even if the original file is deleted; symbolic links break if the original is removed.

Practice

1. What is the main difference between a hard link and a symbolic link in Linux?

easy

A. A hard link can only link to directories; a symbolic link can only link to files.

B. A hard link is a shortcut to a directory; a symbolic link is a shortcut to a file.

C. A hard link points directly to the file's data, sharing the inode; a symbolic link points to the file name.

D. A hard link uses ln -s; a symbolic link uses ln.

Solution

1. Step 1: Understand hard link behavior

   Hard links share the same inode number and point directly to the file data, making them indistinguishable from the original file.

2. Step 2: Understand symbolic link behavior

   Symbolic links are special files that contain a path to another file or directory, acting like shortcuts pointing to file names.

3. Final Answer:

   A hard link points directly to the file's data, sharing the inode; a symbolic link points to the file name. -> Option C

4. Quick Check:

   Hard link = inode sharing, Symbolic link = filename pointer [OK]

Hint: Hard links share inode; symbolic links point to names [OK]

Common Mistakes:

• Confusing which link shares inode
• Thinking symbolic links share file data
• Mixing up commands for creating links

2. Which command correctly creates a symbolic link named linkfile pointing to originalfile?

easy

A. ln -s originalfile linkfile

B. ln linkfile originalfile

C. ln -s linkfile originalfile

D. ln originalfile linkfile

Solution

1. Step 1: Recall symbolic link syntax

   The syntax for creating a symbolic link is ln -s <target> <link_name>.

2. Step 2: Match command to syntax

   ln -s originalfile linkfile uses ln -s originalfile linkfile, which correctly creates a symbolic link named linkfile pointing to originalfile.

3. Final Answer:

   ln -s originalfile linkfile -> Option A

4. Quick Check:

   ln -s target link_name [OK]

Hint: Use ln -s target link_name for symbolic links [OK]

Common Mistakes:

• Swapping target and link name order
• Omitting -s for symbolic links
• Using ln -s with wrong argument order

3. Given the commands:

echo "Hello" > file1
ln file1 file2
ln -s file1 file3
rm file1

What will be the output of cat file2 and cat file3?

medium

A. file2: Hellofile3: Hello

B. file2: cat: file2: No such file or directoryfile3: cat: file3: No such file or directory

C. file2: cat: file2: No such file or directoryfile3: Hello

D. file2: Hellofile3: cat: file3: No such file or directory

Solution

1. Step 1: Understand hard link behavior after deleting original

   Hard link file2 points to the same inode as file1. Removing file1 does not delete the data because file2 still references it. So cat file2 outputs "Hello".

2. Step 2: Understand symbolic link behavior after deleting original

   Symbolic link file3 points to the name file1. After deleting file1, file3 points to a non-existent file, so cat file3 gives an error.

3. Final Answer:

   file2: Hello
   file3: cat: file3: No such file or directory -> Option D

4. Quick Check:

   Hard link survives deletion; symbolic link breaks [OK]

Hint: Hard links keep data after original deleted; symbolic links break [OK]

Common Mistakes:

• Assuming symbolic link still works after target deletion
• Thinking hard link deletes data with original
• Confusing link types' behavior on file removal

4. You run the command ln -s /path/to/file linkname but get an error: ln: failed to create symbolic link 'linkname': File exists. What is the best way to fix this?

medium

A. Delete the target file and rerun the command.

B. Use ln -sf /path/to/file linkname to force overwrite the existing link.

C. Use ln /path/to/file linkname without -s.

D. Rename the target file before creating the link.

Solution

1. Step 1: Understand the error cause

   The error occurs because linkname already exists, and ln refuses to overwrite existing files or links by default.

2. Step 2: Use force option to overwrite

   Using ln -sf forces the symbolic link creation by overwriting the existing linkname safely.

3. Final Answer:

   Use ln -sf /path/to/file linkname to force overwrite the existing link. -> Option B

4. Quick Check:

   ln -sf overwrites existing links safely [OK]

Hint: Use -sf to force overwrite existing symbolic links [OK]

Common Mistakes:

• Deleting the target file instead of the link
• Omitting -s and creating hard link by mistake
• Renaming target unnecessarily

5. You want to create a backup system where multiple filenames point to the same file data without duplicating storage. Which command and link type should you use, and why?

hard

A. Use ln to create hard links because they share the same inode and save space.

B. Use ln -s to create symbolic links because they are easier to manage.

C. Copy the file multiple times to ensure backups are independent.

D. Use ln -s with absolute paths to avoid broken links.

Solution

1. Step 1: Identify storage-saving method

   Hard links share the same inode and file data, so multiple filenames point to the same data without duplicating storage.

2. Step 2: Compare with symbolic links and copies

   Symbolic links only point to filenames and do not save storage if the original is deleted. Copying duplicates data, using more space.

3. Final Answer:

   Use ln to create hard links because they share the same inode and save space. -> Option A

4. Quick Check:

   Hard links save space by sharing inode [OK]

Hint: Hard links share data, saving space for backups [OK]

Common Mistakes:

• Choosing symbolic links for storage saving
• Copying files instead of linking
• Ignoring inode sharing concept