OS/File/System/Link/Hard

• Hard link

  • A hard link is another name for the same underlying file object. On Unix-like file systems, a OS/File/System/Directory maps names to OS/File/System/Inode numbers; multiple hard links are simply multiple directory entries pointing to the same inode, so each name reaches the same file content and metadata.
  • Deleting one hard link removes that directory entry, not necessarily the file data. The file data remains available until the last hard link is removed and no process still has it open.

  • Advantages

    • Same-object identity - Each hard link is an equal name for the same file, rather than a pointer to a preferred target path.
    • Rename and deletion resilience - Other hard links keep working when one name is renamed or removed.
    • No dangling path - A hard link stores no path string — it is a direct name-to-OS/File/System/Inode mapping. There is nothing to go stale: renaming or removing any other hard link to the same inode leaves this one unaffected.

  • Disadvantages

    • Same-file-system limit - Hard links normally cannot cross file-system boundaries because they refer to an object within one file system.
    • Directory restrictions - Ordinary users generally cannot hard-link directories, because directory hard links can create cycles and confuse traversal.
    • Surprising aliasing - Editing through any hard link changes the same underlying file, which can surprise readers who expected a copy.