The ext4, or fourth extended filesystem is a journalled file system that was revealed on October 10, 2006 by Andrew Morton as a compatible improvement to the ext3, featuring support for volumes up to 1024 petabytes and added extent (allocation of an area for a file to use) support. A software developer is a programmer who is concerned with one or more facets of the software development process, a somewhat broader scope of computer programming. ... Andrew Morton is a Linux kernel developer. ... October 10 is the 283rd day of the year (284th in Leap years). ... 2006 (MMVI) is a common year starting on Sunday of the Gregorian calendar. ... Linux (also known as GNU/Linux) is a Unix-like computer operating system. ... In computer engineering, hard disk drive partitioning is the creation of logical divisions upon a hard disk that allows one to apply operating system-specific logical formatting. ... A pebibyte is a unit of information or computer storage. ... An exbibyte (a contraction of exa binary byte) is a unit of information or computer storage, abbreviated EiB. 1 exbibyte = 260 bytes = 1,152,921,504,606,846,976 bytes = 1,024 pebibytes The exbibyte is closely related to the exabyte, which can either be a synonym for exbibyte, or... In computing, a fork is additional data associated with a file system object. ... Most modern file systems have methods of administering permissions or access rights to specific users and groups of users. ... Filesystem-level encryption, is a form of disk encryption where individual files or directories are encrypted by the file system, in contrast to full disk encryption where the entire partition or disk, where the file system resides, is encrypted. ... An operating system (OS) is a computer program that manages the hardware and software resources of a computer. ... A journaling file system is a file system that logs changes to a journal (usually a circular log in a specially-allocated area) before actually writing them to the main file system. ... Andrew Morton is a Linux kernel developer. ... The ext3 or third extended filesystem is a journalled file system that is commonly used by the Linux operating system. ... A petabyte (derived from the SI prefix peta- ) is a unit of information or computer storage equal to one quadrillion (one long scale billiard) bytes. ... An extent is a contiguous area of storage in a computer file system, reserved for a file. ...

It was included in version 2.6.19 of the Linux kernel which was released on November 29, 2006. To meet Wikipedias quality standards, this article or section can be improved by converting lengthy lists to text. ... November 29 is the 333rd (in leap years the 334th) day of the year in the Gregorian Calendar. ... 2006 (MMVI) is a common year starting on Sunday of the Gregorian calendar. ...

The ext4 filesystem is backward compatible with ext3, that is, it can be mounted as an ext3 partition (using 'ext3' as the filesystem type when mounting.) Similarly, mounting an ext3 filesystem as ext4 is also possible (using the 'ext4dev' filesystem type.) However, if the ext4 partition uses extents (one of the major new features of ext4,) backward compatibility and therefore, the ability to mount the filesystem as ext3 is lost. By default, extents are not used; the 'extents' option is explicitly required (e.g. 'mount /dev/sda1 /mnt/point -t ext4dev -o extents'.) An extent is a contiguous area of storage in a computer file system, reserved for a file. ...

See also

• List of file systems
• Comparison of file systems

The following lists identify, characterise and link to fuller information on computer file systems. ... The following tables compare general and technical information for a number of file systems. ...

External links

• Theodore Ts'o's discussion on ext4
• Andrew Morton's announcement of ext4 support
• Ext4 wiki