ext (Extended File System)
ext is the first file system designed specifically for Linux. Introduced in 1992, it laid the foundation for subsequent file systems like ext2, ext3, and ext4. While ext is no longer in use, its historical significance and influence on Linux file systems remain important. Here's a detailed look at the ext file system and its features:
Structure of the ext File System
1. Boot Sector:
The boot sector contains metadata about the file system, including:
Inode Count:Total number of inodes in the file system.
Block Count:Total number of blocks in the file system.
Reserved Block Count:Number of blocks reserved for the root user.
Free Block Count:Number of free blocks available.
Free Inode Count:Number of free inodes available.
First Data Block:Block number of the first data block.
Block Size:Size of each block (commonly 1024 bytes).
2. Inode Structure:
Each file or directory in ext is represented by an inode, which contains:
File Type and Permissions:
Indicates if it's a file, directory, or special type.
File Size:
Size of the file in bytes.
Timestamps:
Tracks file creation, modification, and access times.
Pointers to Data Blocks:
Direct and indirect pointers to the blocks storing file content.
3. Directory Structure:
Directories are implemented as files containing a list of directory entries. Each entry includes:
Inode Number:
Points to the inode representing the file or subdirectory.
Entry Length:
Length of the directory entry.
File Name Length:
Length of the file name.
File Name:
The actual name of the file or subdirectory.
Features of ext
Simplistic Design:
Provided basic file system functionality tailored for Linux.
Support for Inodes:
Allowed efficient indexing of files and directories.
Limitations:
Did not support advanced features like journaling or large files.
Foundation for ext2 and Beyond:
Served as the groundwork for the development of ext2, ext3, and ext4.
Legacy and Historical Significance
The ext file system introduced several key ideas to Linux file system design, such as:
Dynamic Inode Allocation:
Inodes were allocated dynamically to reduce fragmentation.
Improved Directory Management:
Provided better handling of directories compared to older Unix file systems.
While ext has been replaced by more advanced file systems, its impact is still felt in modern Linux storage solutions.
Tools and Commands for ext (Historical Reference)
fsck:Checks and repairs ext file systems.
mkfs.ext:Creates an ext file system (used historically).
mount:Mounts the ext file system.
Example
ext was a stepping stone in Linux's file system evolution. It demonstrated the potential of Linux-specific file systems and paved the way for its successors.