System information

The ext4 file system also supports the following:

Extended attributes (xattr) — This allows the system to associate several additional

name and value pairs per file.

Quota journaling — This avoids the need for lengthy quota consistency checks after a

crash.

Note

The only supported journaling mode in ext4 is d ata= ord ered (default).

Subsecond timestamps — This gives timestamps to the subsecond.

6.1. Creat ing an Ext 4 File Syst em

To create an ext4 file system, use the mkfs. ext4 command. In general, the default options are

optimal for most usage scenarios:

# mkfs. ext4 /d ev/device

Below is a sample output of this command, which displays the resulting file system geometry and

features:

Examp le 6 .1. mkfs. ext4 co mman d o u t p u t

~]# mkfs.ext4 /dev/sdb1

mke2fs 1.41.12 (17-May-2010)

Filesystem label=

OS type: Linux

Block size=4096 (log=2)

Fragment size=4096 (log=2)

Stride=0 blocks, Stripe width=0 blocks

245280 inodes, 979456 blocks

48972 blocks (5.00%) reserved for the super user

First data block=0

Maximum filesystem blocks=1006632960

30 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

Writing inode tables: done

Creating journal (16384 blocks): done

Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 20 mounts or

180 days, whichever comes first. Use tune2fs -c or -i to override.

⁠Chapt er 6 . T he Ext 4 File Syst em