Understanding Linux File Storage: Inodes, Blocks, and Links Explained

File storage in Linux

Linux stores a file in three separate places: the inode holds the file's metadata, the block area stores the actual file data, and the directory entry (a special block) maps the file name to its inode number.

Metadata stored in an inode

inode number (unique identifier)

file type

permissions

size

owner and group

UID and GID

three timestamps (access, modify, change)

link count

File creation process

Allocate a free inode number.

Write the file’s metadata into the inode area.

Allocate data blocks of the required size and store the file’s contents.

File deletion process

The core step is to remove the mapping between the directory entry and the inode, so the file name no longer appears in the directory.

Hard and soft links

Both are part of a file’s attributes and provide additional references without duplicating the file’s data.

Hard links

A hard link creates another pathname that points directly to the same inode.

Cannot be created across different file systems (e.g., ext4 to xfs).

Cannot be created for directories except for the special entries . (current directory) and .. (parent directory).

Soft (symbolic) links

A soft link works like a Windows shortcut and stores a path to the target file.

Can cross partitions and file systems.

Can point to directories.

If the link name is omitted, it defaults to the source file’s name.

When using a relative path, the stored path is relative to the link’s location, not the source file.

Creating links in Linux

# Create a hard link
sudo ln file_name new_file_name

# Create a soft link
sudo ln -s file_name new_file_name

Example:

ehigh@ubuntu:~$ sudo ln general.conf general_1.conf

ehigh@ubuntu:~$ sudo ln -s general.conf general_2.conf

Using relative paths correctly

Given the directory layout:

/home/user/
│
├── docs/
│   └── file.txt
│
└── links/

Creating a link with an incorrect relative path:

# Incorrect
ln -s docs/file.txt links/link_to_file

This creates a link that points to links/docs/file.txt, which is wrong.

Correct command: ln -s ../docs/file.txt links/link_to_file Using an absolute path for the source is recommended to avoid such errors.

Link count details

When a file is created, its hard link count starts at 2 because the directory entry . (the file itself) and the parent directory’s entry both reference it. . – refers to the current directory. .. – refers to the parent directory.