At what hard link count is a file effectively deleted?

• A. 0
• B. 1
• C. 2
• D. 3

Answer: (A)

The important idea is that a file’s existence in the filesystem is tied to references to its inode. A hard link count tells you how many directory entries point to that inode. A file exists as long as there is at least one directory entry referencing it or at least one open file descriptor referring to it. When all directory entries that reference the file are removed, the hard link count drops to zero. At that moment, there is no name left in the filesystem that refers to that inode, so the file is effectively deleted from the namespace. The actual disk space is only reclaimed after the last open handle to the file is closed, but the moment the link count becomes zero, it is no longer accessible by any name. So zero is the point at which the file is effectively deleted.