What is Ext2, Ext3 & Ext4 and How to Create and Convert Linux File Systems

File system is divided in two segments called User Data and Metadata. In this article I am trying to explore how to create and convert various Linux file systems and high level difference amongst Ext2, Ext3 and Ext4 file systems. Before moving further readings, let me introduce a brief about Linux file systems.

Linux File System

Ext2 – Second Extended File System

  1. Ext2 file system was introduced in 1993 and Ext2 was developed by Remy Card. It was the first default file system in several Linux distro like RedHat and Debian.
  2. It was to overcome limitation of legacy Ext file system.
  3. Maximum file size is 16GB – 2TB.
  4. Journaling feature is not available.
  5. It’s being used for normally Flash based storage media like USB Flash drive, SD Card etc.

Ext3 – Third Extended File System

  1. Ext3 file system was introduced in 2001 and same was integrated in Kernel 2.4.15 with journaling feature, which is to improve reliability and eliminates need to check file system after unclean shutdown.
  2. Max file size 16GB – 2TB.
  3. Provide facility to upgrade from Ext2 to Ext3 file systems without having to back up and restore data.

Ext4 – Fourth Extended File System

  1. Ext4, the high-anticipated Ext3 successor.
  2. On October 2008, Ext4 as stable code were merged in the Kernel 2.6.28 which contains Ext4 file system.
  3. Backward compatibility.
  4. Max file size 16GB to 16TB.
  5. Ext4 file system have option to Turn Off journaling feature.
  6. Other features like Sub Directory Scalability, Multiblock Allocation, Delayed Allocation, Fast FSCK etc.