Ext4
ext4 (第四代 扩展文件系统 ) 是 一个开源的磁盘 文件系统 并且是扩展系列文件系统的最新版本。它是许多 Linux 系统使用的主文件系统，这使其成为 Linux 中可以说是支持最稳定且经过良好测试的文件系统。
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.
安装
内核
激活以下内核选项来启用 ext4 支持：
File systems --->
<*> The Extended 4 (ext4) filesystem
可选的 ext4 特性支持：
File systems --->
[*] Ext4 POSIX Access Control Lists
[*] Ext4 Security Labels
[ ] EXT4 debugging support
The ext4 filesystem code can 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.
Both ext2 and ext3 file timestamps are affected by the year 2038 problem , while ext4 is Y2k38-safe since 2016, Linux kernel 4.3.6 and e2fsprogs 1.43.
Ext3
The original ext3 filesystem code was removed from the Linux kernel with version 4.3. There should remain only rare cases which make it necessary to use an ext3 filesystem, in which case the ext4 filesystem driver may be used.
Activate the following kernel options for ext3 support:
File systems --->
<*> Ext3 journalling file system support
Support for optional ext3 features:
File systems --->
[*] Default to 'data=ordered' in ext3
[*] Ext3 extended attributes
[*] Ext3 POSIX Access Control Lists
[*] Ext3 Security Labels
Ext2
The ext2 filesystem does not have journaling support .
Even though the ext2 filesystem code remains available, it is advised to use the ext4 driver to mount ext2 filesystems. Under those normal circumstances the ext2 driver should not be enabled.
The original ext2 filesystem code remains available for special cases. For example: compared to the ext4 filesystem code, the original ext2 code has a lower memory footprint.
Activate the following kernel options for ext2 support:
File systems --->
<*> Second extended fs support
Support for optional ext2 features:
File systems --->
[*] Ext2 extended attributes
[*] Ext2 POSIX Access Control Lists
[*] Ext2 Security Labels
大型设备支持
-*- Enable the block layer --->
[*] Support for large (2TB+) block devices and files
USE 标记
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/e2fsprogs
使用
创建
mkfs.ext4 命令不可恢复地破坏了要格式化的分区所有内容。请确保您选择了正确的分区！
在 /dev/sda1 分区创建一个 ext4 文件系统：
root
#
mkfs.ext4 /dev/sda1
Mounting
See filesystem .
Utilities
Utilities included in the package consist of:
| Utility | Description | Man page |
|---|---|---|
| badblocks | A small program for stress testing block devices. | badblocks(8) |
| debugfs | An ext2/ext3/ext4 file system debugger. | debugfs(8) |
| dumpe2fs | A tool to dump ext2/ext3/ext4 filesystem information. | dumpe2fs(8) |
| e2fsck | A tool for checking ext2/ext3/ext4 filesystems. | e2fsck(8) |
| e2image | A tool for saving critical ext2/ext3/ext4 filesystem metadata to a file. | e2image(8) |
| 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. | e2undo(8) |
| 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. | logsave(8) |
| mke2fs | The base program for creating ext2/ext3/ext4 filesystems. Creation commands symlink here. | mke2fs(8) |
| 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. | resize2fs(8) |
| tune2fs | Adjust tunable filesystem parameters on ext2/ext3/ext4 filesystems. | tune2fs(8) |
| chattr | Change file attributes on a Linux filesystem. | chattr(1) |
| lsattr | List ext2/ext3/ext4 file attributes. | lsattr(1) |
| e2freefrag | Report free space fragmentation information. | e2freefrag(8) |
| e4defrag | An online defragmenter for ext4 filesystem. | e4defrag(8) |
| filefrag | Report on file fragmentation. | filefrag(8) |
| mklost+found | Create a lost+found directory on a mounted ext2/ext3/ext4 file system. | mklost+found(8) |
另请参阅
- Ext4 encryption — provides instructions on encrypting files in a home partition using the ext4 filesystem's built-in file based encryption.
- JFS — 一个由 IBM 创造的 64 位日志 文件系统
- Btrfs — 一个写入时复制(CoW) 的 Linux 文件系统 ，旨在实现高级功能的同时专注于容错、修复和易于管理等功能。
- XFS — 一个高性能日志 文件系统
- F2FS — 一个为基于 NAND 闪存设备设计的 文件系统 。