ext4 (fourth extended file system) is an open source disk filesystem and most recent version of the extended series of filesystems. It is the primary file system in use by many Linux systems rendering it to be arguably the most stable and well tested file system supported in Linux.
Initially created as a fork of ext3, ext4 brings new features, performance improvements, and removal of size limits with moderate changes to the on-disk format. It can span volumes up to 1 EB and with maximum file size of 16TB. Instead of the classic ext2/3 bitmap block allocation, ext4 uses extents, which improve large file performance and reduce fragmentation. Ext4 also provides more sophisticated block allocation algorithms (delayed allocation and multiblock allocation) giving the filesystem driver more ways to optimize the layout of data on the disk.
Activate the following kernel options for ext4 support:
File systems ---> <*> The Extended 4 (ext4) filesystem
Support for optional ext4 features:
File systems ---> [*] Ext4 POSIX Access Control Lists [*] Ext4 Security Labels [ ] EXT4 debugging support
|Ext4 POSIX Access Control Lists||Enable ACL permissions.|
|Ext4 Security Labels||Enable POSIX capabilities support.|
|EXT4 debugging support||(Not recommend) Use when debugging ext4 (advanced users only).|
Large drive support
When the system has large disks (2 TB or greater) and a 32-bit (x86) kernel is being used, the following option must be enabled:
-*- Enable the block layer ---> [*] Support for large (2TB+) block devices and files
USE flags for sys-fs/e2fsprogs Standard EXT2/EXT3/EXT4 filesystem utilities
||Install e2scrub_all cron script|
||Build fuse2fs, a FUSE file system client for ext2/ext3/ext4 file systems|
||Add Native Language Support (using gettext - GNU locale utilities)|
||Enable behavior to support maintaining /bin, /lib*, /sbin and /usr/sbin separately from /usr/bin and /usr/lib*|
||Build static versions of dynamic libraries as well|
||Enable dependencies and/or preparations necessary to run tests (usually controlled by FEATURES=test but can be toggled independently)|
||Build extfs tools (mke2fs, e2fsck, tune2fs, etc.)|
After setting the USE flag update the system so the changes take effect:
emerge --ask --changed-use --deep @world
The mkfs.ext4 command irreversibly destroys any content of the partition it is told to format. Be sure to select the right partition!
To create an ext4 filesystem on the /dev/sda1 partition:
Please replace /dev/sda1 with the actual partition to format.
By default, 5% of available disk space is reserved for the root user. This is usually a good thing for the partition where the / directory is mounted, but it may be not desirable on other partitions. To lose reserve disk space for the root user use mkfs.ext4's
-m 0 option:
mkfs.ext4 -m 0 /dev/sda1
- Ext4 encryption — provides instructions on encrypting files in a home partition using the ext4 filesystem's built-in file based encryption.
- JFS — a 64-bit journaling filesystem created by IBM.
- Btrfs — a copy-on-write (CoW) filesystem for Linux aimed at implementing advanced features while focusing on fault tolerance, self-healing properties, and easy administration.
- XFS — a high-performance journaling filesystem
- F2FS — a filesystem designed for NAND flash-based devices.