Installation guide
Chapter 7. The Ext4 File System
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7.1. Creating an Ext4 File System
To create an ext4 file system, use the mkfs.ext4 command. In general, the default options are
optimal for most usage scenarios, as in:
mkfs.ext4 /dev/device
Below is a sample output of this command, which displays the resulting file system geometry and
features:
mke2fs 1.41.9 (22-Aug-2009)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
1954064 inodes, 7813614 blocks
390680 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=4294967296
239 block groups
32768 blocks per group, 32768 fragments per group
8176 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
4096000
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done
For striped block devices (e.g. RAID5 arrays), the stripe geometry can be specified at the time of file
system creation. Using proper stripe geometry greatly enhances performance of an ext4 file system.
When creating file systems on lvm or md volumes, mkfs.ext4 chooses an optimal geometry. This
may also be true on some hardware RAIDs which export geometry information to the operating
system.
To specify stripe geometry, use the -E option of mkfs.ext4 (i.e. extended file system options) with
the following sub-options:
stride=value
Specifies the RAID chunk size.
stripe-width=value
Specifies the number of data disks in a RAID device, or the number of stripe units in the stripe.
For both sub-options, value must be specified in file system block units. For example, to create a file
system with a 64k stride (i.e. 16 x 4096) on a 4k-block file system, use the following commmand:
mkfs.ext4 -E stride=16,stripe-width=64 /dev/device
For more information about creating file systems, refer to man mkfs.ext4.