Sysadmin Linux Theory

Symbolic_vs__Hard_Links

Comparing symbolic and hard links, their differences, use cases, and practical implementation

Links in Linux are references to files that allow multiple names to point to the same data. Understanding symbolic (soft) and hard links is crucial for file management, backup strategies, and system administration.

Key Concepts

  • Hard Link: Direct reference to file data on disk
  • Symbolic Link: Pointer containing path to another file
  • Inode: File system structure storing file metadata
  • Link Count: Number of hard links pointing to file data
  • Dangling Link: Symbolic link pointing to non-existent file

Command Syntax

ln [options] target linkname

  • Creates links between files
  • Default creates hard links
  • Use -s for symbolic links

Common Options

-s - Create symbolic (soft) link -f - Force creation, overwrite existing -v - Verbose output -i - Interactive, prompt before overwrite

Practical Examples 

1
2

ln original.txt hardlink.txt
ls -li original.txt hardlink.txt

Both files share same inode number and data

1
2

ln -s /path/to/original.txt symlink.txt
ls -l symlink.txt

Shows arrow pointing to target file

1

stat original.txt

Displays inode, links count, and file info

1

ln -s /home/user/file.txt /tmp/link.txt

Symbolic links work across different filesystems

Key Differences

  • Share same inode and disk space
  • Cannot span filesystems
  • Cannot link to directories
  • Original file deletion doesn’t break link
  • No visual indication in ls -l
  • Have separate inode
  • Can span filesystems
  • Can link to directories
  • Break if target is deleted
  • Show as link -> target in ls -l

Use Cases

  • Backup files without duplicating space
  • Multiple access points to same data
  • Prevent accidental file deletion
  • File versioning systems
  • Create shortcuts to frequently used files
  • Link across different filesystems
  • Point to directories
  • Configuration file management
  • Application path management

ls -l - Show symbolic links with arrows ls -i - Display inode numbers find -type l - Find symbolic links readlink - Show symbolic link target unlink - Remove links

Tips & Troubleshooting

Common Issues

  • Broken symbolic links: Use find -xtype l to locate
  • Permission denied: Check target file permissions
  • Cross-device links: Use symbolic links instead

Best Practices

  • Use absolute paths for system-wide symbolic links
  • Use relative paths for portable link structures
  • Document important symbolic links
  • Regular cleanup of broken links

Security Notes

  • Symbolic links can create security vulnerabilities
  • Be cautious with links in world-writable directories
  • Verify link targets before following them
  • Use ls -L to follow symbolic links

Verification Commands 

1
2
3
4
5
6
7
8

# Check if file is a symbolic link
test -L filename && echo "Symbolic link"

# Count hard links to a file  
ls -l filename | awk '{print $2}'

# Find all hard links to a file
find / -inum $(stat -c %i filename) 2>/dev/null