File System: ext2

File System: ext2

ext2The ext2 file system is one of the oldest Linux file systems still available. The acronym ext2 stands for “Second Extended File System.” Originally introduced back in 1993, ext2 stores data in the standard hierarchical fashion used by most other file systems. Data is stored in files; files are stored in directories. A directory can contain either files or other directories (subdirectories).



The maximum file size supported in the ext2 file system is 2TB (terabytes). An ext2 volume can be up to 4TB. File names can be up to 255 characters long. The ext2 file system supports Linux file system users, groups, and permissions (called POSIX permissions). It also supports file compression.

In fact, it’s probably the most widely used Linux file system ever implemented. It’s also reputed to be the fastest Linux file system available.



ext2 takes a long time to recover if the system shuts down abruptly. When shutting down the Linux system, the operating system first cleanly dismounts the file system, ensuring all pending file system transactions are written to disk before the system shuts off.



The problem arises when the system halts without completing this clean dismount procedure. For example, suppose a power outage occurs and the Linux system shuts off suddenly without going through the proper shutdown procedure. When this happens, it is possible that pending disk transactions weren’t completed.



To clean up the file system, the ext2 file system will automatically run a program called e2fsck the next time the system is booted.


The issue here is that e2fsck will analyze the entire file system when this happens, not just the last few files that were in the process of being modified.


On a basic Linux system, this can take from 10 to 15 minutes. On an extensive system that has a lot of file system data (such as a network file server), this process can take several hours.