Information Technology Reference
In-Depth Information
Extended File System - EXT
Extended File System (EXT), which was introduced in 1992 specifically for the Linux ker-
nel, was one of the first file systems and used the virtual file system. EXT2, EXT3, and
EXT4 are the subsequent versions. Journaling is the main advantage of EXT3 over EXT2.
With EXT3, in case of an unexpected shutdown, there is no need to verify the file system.
the EXT4 file system, the fourth extended file system, has gained significance with mobile
devices implementing dual-core processors. The YAFFS2 file system is known to have a
bottleneck on dual-core systems. With the Gingerbread version of Android, the YAFFS file
system was swapped for EXT4. The following are the mount points that use EXT4 on Sam-
sung Galaxy S3 mobile:
/dev/block/mmcblk0p9 /system ext4
ro,noatime,barrier=1,data=ordered 0 0
/dev/block/mmcblk0p3 /efs ext4
rw,nosuid,nodev,noatime,barrier=1,journal_async_commit,data=ordered
0 0
/dev/block/mmcblk0p8 /cache ext4
rw,nosuid,nodev,noatime,barrier=1,journal_async_commit,data=ordered
0 0
/dev/block/mmcblk0p12 /data ext4
rw,nosuid,nodev,noatime,barrier=1,journal_async_commit,data=ordered,noauto_da_alloc,discard
0 0
VFAT
is an extension to the FAT16 and FAT32 file systems. Microsoft's FAT32 file system
is supported by most Android devices. It is supported by almost all the major operating sys-
tems, including Windows, Linux, and Mac OS. This enables these systems to easily read,
modify, and delete the files present on the FAT32 portion of the Android device. Most of
the external SD cards are formatted using the FAT32 file system. Observe the following
output, which shows that the mount points
/sdcard
and
/secure/asec
use the VFAT
file system.
shell@Android:/sdcard $ mount
mount
rootfs / rootfs rw 0 0
tmpfs /dev tmpfs rw,nosuid,relatime,mode=755 0 0
devpts /dev/pts devpts rw,relatime,mode=600,ptmxmode=000 0 0
proc /proc proc rw,relatime 0 0
sysfs /sys sysfs rw,relatime 0 0
