In Linux, every file is associated with an inode—an index node storing metadata such as size, timestamps, ownership, and a pointer to the actual data blocks. The inode serves as the true identifier for a file; filenames are merely references. File contents reside in data blocks referenced via their inode.

List a file's inode using ls -i:

$ ls -i
31615656 AndroidStudioProjects  30836545 go
1152719 Applications            49115578 images
31827389 CNode                   13208576 ktsgs.zip
  595399 Desktop                 44722768 pandoc_demo
  595275 Documents               49218456 pgadmin.log
  595277 Downloads               15078624 pomelo
 7094352 LevelTest               1009499 project
 7098493 LevelTest.zip           1011801 qdb
  595388 Library                 5901898 qdb.zip
  595439 Movies                  23150187 test
  595441 Music                   1010768 tmp
  595443 Pictures               17956310 trunk
  595445 Public                 17970255 trunk.zip
32072972 app                     41999857 webwork
 1009500 code                    13208610 游戏配置
22509232 databak

The leading number on each line is the inode value.

Linking mechanisms provide alternate access paths to a file, similar to shortcuts in Windows, implemented via the ln command.

Command syntax:

ln [option] target_path link_name

Options:

• -f — Force removal of existing destination files before linking.
• -i — Prompt before overwriting an existing file.

Symbolic Link (Soft Link)

Create with:

ln -s src_file sym_link

A symbolic link is an independent file with its own inode. Its data block stores the pathname of the target file rather than the file's actual contents. Characteristics:

• Each symbolic link possesses a distinct inode.
• Can reference both regular files and directories.
• May span different filesystems.
• Removing the link leaves the target intact; deleting the target renders the link unusable (dangling).

Hard Link

Create with:

ln src_file hard_link

A hard link creates an additional directory entry pointing to the same inode and physical data as the original file. Apart from the name, it shares all metadata and content with the source. Essentially, the file acquires an additional filename.

Charatceristics:

• Shares the identical inode with the original file.
• Referencse the exact same data blocks.
• Can only be created for existing regular files (not directories).
• Removing one link does not affect others; data persists until all links are removed.
• Limited to the same filesystem.