Analyze the physical organization of the Linux ext2 file system

Linux ext2 file system is one of the commonly used file systems in Linux operating systems and has good performance and stability. This article will analyze the physical organization of the ext2 file system in detail and provide some specific code examples to help readers better understand.

1. Overview of ext2 file system

The ext2 file system is the earliest second-generation extended file system on the Linux system. It has made great achievements in the performance, reliability and stability of the file system. Certain improvements. It mainly consists of super block, group descriptor, index node table (inode table), and data block. In the ext2 file system, data and metadata are stored in blocks, and the minimum storage unit of the file system is blocks instead of bytes.

2. Physical Organization

1. Super Block: The super block is a key structure in the ext2 file system, which stores important information of the entire file system, such as blocks The total number of free blocks, the total number of index nodes, etc. It is usually located in the first block of the file system and is shared by the entire file system.
2. Group Descriptor: The group descriptor is a structure that divides the entire file system into several groups. Each group contains a certain number of data blocks and index nodes. Each group descriptor records some important information in the group, such as the number of free blocks, the number of free index nodes, etc.
3. Inode Table: The index node table stores metadata information of all files and directories, such as file size, permissions, last modification time, etc. Each index node corresponds to a file or directory and has a unique index number.
4. Data Block: The data block is the key part of storing file data. All file data in the file system is stored in the data block. Data blocks can be logical blocks (logical block size is configurable) or physical blocks (usually the same size as disk sectors).

Sample code:

#include <stdio.h>
#include <fcntl.h>
#include <ext2fs/ext2_fs.h>

int main() {
    int fd = open("/dev/sda1", O_RDONLY);
    struct ext2_super_block super_block;

    lseek(fd, 1024, SEEK_SET);
    read(fd, &super_block, sizeof(super_block));

    printf("Total blocks: %lu
", super_block.s_blocks_count);
    printf("Free blocks: %lu
", super_block.s_free_blocks_count);

    close(fd);
    return 0;
}

The above sample code demonstrates how to read the super block information of the ext2 file system in C language, where "/dev/sda1" is the location of the file system device files. Reading superblock information can help us understand important information such as the capacity and remaining space of the entire file system.

In summary, the physical organization of the Linux ext2 file system is based on the block mechanism to organize file data and metadata, and the entire file is managed through structures such as super blocks, group descriptors, and index node tables. System storage space and metadata. Through the above code examples, readers can have a deeper understanding of the physical organization and related operations of the ext2 file system.

The above is the detailed content of Analyze the physical organization of the Linux ext2 file system. For more information, please follow other related articles on the PHP Chinese website!