Ext4
From Gentoo Wiki
Outdated translations are marked like this.
ext4 (fjärde extended file system) är det nyaste filsystemet av extended-serien med öppen källkod. Det är det primära filsystemet på många Linux-system och är utan tvekan det mest stabila och välfungerande filsystemet som stöds av 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.
Installation
Linux-kärnan
Aktivera följande kärnalternativ för ext4-stöd:
KERNEL Aktivera stöd för ext4
File systems --->
<*> The Extended 4 (ext4) filesystem
Stöd för frivilliga ext4-funktioner:
KERNEL Enabling optional features for ext4
File systems --->
[*] Ext4 POSIX Access Control Lists
[*] Ext4 Security Labels
[ ] EXT4 debugging support
Ext3
Note
A normal ext4 system will not need to enable ext3 or ext2 options. These options are here solely for historical purposes.
A normal ext4 system will not need to enable ext3 or ext2 options. These options are here solely for historical purposes.
Activate the following kernel options for ext3 support:
KERNEL Enabling ext3 support
File systems --->
<*> Ext3 journalling file system support
Support for optional ext3 features:
KERNEL Enabling ext3 features
File systems --->
[*] Default to 'data=ordered' in ext3
[*] Ext3 extended attributes
[*] Ext3 POSIX Access Control Lists
[*] Ext3 Security Labels
Ext2
Note
Ext2 does not have journaling, support for this was added in Ext3
Ext2 does not have journaling, support for this was added in Ext3
Activate the following kernel options for ext2 support:
KERNEL Enabling ext2 support
File systems --->
<*> Second extended fs support
Support for optional ext2 features:
KERNEL Enabling ext2
File systems --->
[*] Ext2 extended attributes
[*] Ext2 POSIX Access Control Lists
[*] Ext2 Security Labels
Note
The original ext3 filesystem code was removed from the Linux Kernel with version 4.3, instead the ext4 filesystem code can now handle ext2, ext3 and ext4 filesystems. It will maintain compatibility if the filesystem is mounted as ext2 or ext3, and will provide upgradability when mounted as ext4. Additionally tune2fs can be used to add ext3- and ext4-specific features to an existing ext2 or ext3 filesystem, though certain hard limits will remain.
The original ext2 filesystem code remains available.
The original ext3 filesystem code was removed from the Linux Kernel with version 4.3, instead the ext4 filesystem code can now handle ext2, ext3 and ext4 filesystems. It will maintain compatibility if the filesystem is mounted as ext2 or ext3, and will provide upgradability when mounted as ext4. Additionally tune2fs can be used to add ext3- and ext4-specific features to an existing ext2 or ext3 filesystem, though certain hard limits will remain.
The original ext2 filesystem code remains available.
Note
Both ext2 and ext3 file timestamps are affected by the year 2038 problem, while ext4 is Y2k38-safe since 2016, Kernel 4.3.6 and e2fsprogs 1.43.
Both ext2 and ext3 file timestamps are affected by the year 2038 problem, while ext4 is Y2k38-safe since 2016, Kernel 4.3.6 and e2fsprogs 1.43.
Large drive support
KERNEL Enabling large drives for x86 kernels
-*- Enable the block layer --->
[*] Support for large (2TB+) block devices and files
USE flags
USE flags for sys-fs/e2fsprogs Standard EXT2/EXT3/EXT4 filesystem utilities
+tools
|
Build extfs tools (mke2fs, e2fsck, tune2fs, etc.) |
archive
|
Add support for mke2fs to read a tarball as input. This allows not needing privileges. Needs app-arch/libarchive. |
cron
|
Install e2scrub_all cron script |
fuse
|
Build fuse2fs, a FUSE file system client for ext2/ext3/ext4 file systems |
nls
|
Add Native Language Support (using gettext - GNU locale utilities) |
static-libs
|
Build static versions of dynamic libraries as well |
test
|
Enable dependencies and/or preparations necessary to run tests (usually controlled by FEATURES=test but can be toggled independently) |
Emerge
The sys-fs/e2fsprogs package and should be available as part of the default system set.
root #emerge --ask sys-fs/e2fsprogsUsage
Creation
Warning
The mkfs.ext4 command irreversibly destroys any content of the partition it is told to format. Be sure to select the right partition!
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/sda1Mounting
See filesystem.
Utilities
Utilities included in the package consist of:
| Utility | Description | Man page |
|---|---|---|
| badblocks | A small program for stress testing block devices. | Man page |
| debugfs | An ext2/ext3/ext4 file system debugger. | Man page |
| dumpe2fs | A tool to dump ext2/ext3/ext4 filesystem information. | Man page |
| e2fsck | A tool for checking ext2/ext3/ext4 filesystems. | Man page |
| e2image | A tool for saving critical ext2/ext3/ext4 filesystem metadata to a file. | Man page |
| e2label | A tool to change the label on an ext2/ext3/ext4 filesystem (symlinks to tune2fs). | |
| e2undo | A tool to replay an undo log for an ext2/ext3/ext4 filesystem. | Man page |
| fsck.ext2 | Checks, specifically, an ext2 filesystem (symlinks to e2fsck). | |
| fsck.ext3 | Checks, specifically, an ext3 filesystem (symlinks to e2fsck). | |
| fsck.ext4 | Checks, specifically, an ext4 filesystem (symlinks to e2fsck). | |
| fsck.ext4dev | Checks, specifically, an ext4dev filesystem (symlinks to e2fsck). | |
| logsave | A tool to save the output of a command in a logfile. | Man page |
| mke2fs | The base program for creating ext2/ext3/ext4 filesystems. Creation commands symlink here. | Man page |
| mkfs.ext2 | Creates, specifically, an ext2 filesystem (symlinks to mke2fs). | |
| mkfs.ext3 | Creates, specifically, an ext3 filesystem (symlinks to mke2fs). | |
| mkfs.ext4 | Creates, specifically, an ext4 filesystem (symlinks to mke2fs). | |
| mkfs.ext4dev | Creates, specifically, an ext24dev filesystem (symlinks to mke2fs). | |
| resize2fs | An ext2/ext3/ext4 filesystem resizer. | Man page |
| tune2fs | Adjust tunable filesystem parameters on ext2/ext3/ext4 filesystems. | Man page |
| Utility | Description | Man page |
|---|---|---|
| chattr | Change file attributes on a Linux filesystem. | Man page |
| lsattr | List file attributes on a Linux second extended filesystem. | Man page |
| Utility | Description | Man page |
|---|---|---|
| e2freefrag | Report free space fragmentation information. | Man page |
| e4defrag | An online defragmenter for ext4 filesystem. | Man page |
| filefrag | Report on file fragmentation. | Man page |
| mklost+found | Create a lost+found directory on a mounted Linux second extended filesystem. | Man page |
See also
- XFS — a high-performance journaling filesystem
- Btrfs — ett copy-on-write (CoW) filsystem för Linux som syftar till att införa avancerade funktioner jämsides feltolerans, självläkande egenskaper och enkel administration.
- FAT — filesystem originally created for use with MS-DOS (and later pre-NT Microsoft Windows).
External resources
- https://ext4.wiki.kernel.org/ - The second, third, and fourth extended file system wiki.
- https://bugzilla.kernel.org/show_bug.cgi?id=23732 - The final fix for the Year 2038 problem, only for ext4.