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What is inode?

To understand inode, start with file storage.

Files are stored on the hard disk, and the smallest storage unit of the hard disk is called the "Sector". Each sector stores 512 bytes (equivalent to 0.5KB).

When the operating system reads the hard disk, it does not read sector by sector, which is too inefficient, but reads multiple sectors in succession at one time, that is, reading a "block" at one time. This "block", which consists of multiple sectors, is the smallest unit of file access. The most common size of a "block" is 4KB, that is, eight consecutive sector form a block.

File data is stored in "blocks", so obviously we must also find a place to store the "meta-information" of the file, such as the creator of the file, the date the file was created, the size of the file, and so on. The area where the meta-information of the file is stored is called inode, which is translated into Chinese as "index node".

Each file has a corresponding inode, which contains some information about the file.

II. The content of inode

1.inode contains the meta-information of the file, specifically, the following:

Number of bytes in the file

User ID of the file owner

Group ID of the file

Read, write and execute permissions of files

There are three timestamps for the file:

Ctime refers to the time when the file's properties were last changed.

Atime refers to the time when the file was last accessed

Mtime refers to the time when the file was last modified.

two。 You can use the stat command to view the inode information of a file

3. View only inode numbers

4. View file types

5. Link file

Hard link: the indoe number is the same as the source file

Soft connection: the number is different, but the idone number points to the name of the source file

6.inode node

(1)。 View Node

(2)。 Every time a file is created, the number of nodes is increased by 1. When the nodes are full, the file cannot be created even if there is memory.

7. Delete files by inode number

Find. / *-inum number-delete

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