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7.3. Mounting an Ext4 File System

An ext4 file system can be mounted with no extra options. For example:
mount /dev/device /mount/point
The ext4 file system also supports several mount options to influence behavior. For example, the acl parameter enables access control lists, while the user_xattr parameter enables user extended attributes. To enable both options, use their respective parameters with -o, as in:
mount -o acl,user_xattr /dev/device /mount/point
The tune2fs utility also allows administrators to set default mount options in the file system superblock. For more information on this, refer to man tune2fs.

Write Barriers

By default, ext4 uses write barriers to ensure file system integrity even when power is lost to a device with write caches enabled. For devices without write caches, or with battery-backed write caches, disable barriers using the nobarrier option, as in:
mount -o nobarrier /dev/device /mount/point
For more information about write barriers, refer to Chapter 16, Write Barriers.

Mounting an Ext3 File System as Ext4

An ext3 file system can also be mounted as ext4 without changing the format, allowing it to be mounted as ext3 again in the future. To do so, run the following command (where device is an ext3 file system):
mount -t ext4 /dev/device /mount/point
Doing so will only allow the ext3 file system to use ext4-specific features that do not require a file format conversion. These features include delayed allocation and multi-block allocation, and exclude features such as extent mapping.
For more information about mounting an ext4 file system, refer to man mount.