Ext4

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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.

Installation[edit | edit source]

Kernel[edit | edit source]

Activate the following kernel options for ext4 support:

KERNEL Enabling ext4 support
File systems  --->
   <*> The Extended 4 (ext4) filesystem

Support for optional ext4 features:

KERNEL Enabling optional features for ext4
File systems  --->
   [*]   Ext4 POSIX Access Control Lists
   [*]   Ext4 Security Labels
   [ ]   EXT4 debugging support
Optional ext4 support definitions
Option Description
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[edit | edit source]

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:

KERNEL Enabling large drives for x86 kernels
-*- Enable the block layer  --->
    [*]   Support for large (2TB+) block devices and files

USE flags[edit | edit source]

The sys-fs/e2fsprogs package contains the utilities to work with the filesystem. In Gentoo Linux sys-fs/e2fsprogs is part of the system set and should be already installed on the system.

USE flags for sys-fs/e2fsprogs Standard EXT2/EXT3/EXT4 filesystem utilities

cron Install e2scrub_all cron script
fuse Build fuse2fs, a FUSE file system client for ext2/ext3/ext4 file systems
lto Build with link time optimization (LTO)
nls Add Native Language Support (using gettextGNU locale utilities)
split-usr Enable behavior to support maintaining /bin, /lib*, /sbin and /usr/sbin separately from /usr/bin and /usr/lib*
static-libs Build static versions of dynamic libraries as well
threads Add threads support for various packages. Usually pthreads
Data provided by the Gentoo Package Database · Last update: 2021-03-16 16:42 More information about USE flags

Emerge[edit | edit source]

After setting the USE flag update the system so the changes take effect:

root #emerge --ask --changed-use --deep @world

Usage[edit | edit source]

Creation[edit | edit source]

Warning
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:

root #mkfs.ext4 /dev/sda1

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:

root #mkfs.ext4 -m 0 /dev/sda1

See also[edit | edit source]

  • 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, repair, and easy administration.
  • XFS — a high-performance journaling filesystem
  • F2FS — a filesystem designed for NAND flash-based devices.

External resources[edit | edit source]

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