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Storage Partitions
The layout of the MMC/SD card or eMMC for Android system is showed below.
• [Partition type/index] is defined in the MBR.
• [Name] is only meaningful in android, you can ignore it when creating these partitions.
• [Start Offset] shows where partition is started, unit in MBytes.
The SYSTEM partition is used to put the established android system image. The DATA is used
to put application's unpacked codes/data, the database of system configurations, etc. In the
normal boot mode, the root file system is mounted from uRamdisk. In the recovery mode, the
root file system is mounted from the REOVERY partition.
Partition
Name
Start Offset
Type/Index
N/A
BOOT
0
Primary 1
MEDIA
10MB
Primary 2
SYSTEM
follow MEDIA
Logic 5
DATA
follow SYSTEM > 200MB
(Extended 3)
Logic 6
CACHE
follow DATA
(Extended 3)
Primary 4
RECOVERY follow CACHE
To create these partitions, you can simply use the MFG tool described in the next section, or
use the fdisk utility on Linux PC.
After creating the partition by fdisk, please format each file system via the following
commands:
# mkfs.vfat /dev/sdx1
# mkfs.ext4 /dev/sdx2 -O ^extent -L system
# mkfs.ext4 /dev/sdx4 -O ^extent -L recovery
# mkfs.ext4 /dev/sdx5 -O ^extent -L data
# mkfs.ext4 /dev/sdx6 -O ^extent -L cache
Appendix A BSP User Guide
Appendix A
Size
File System
Content
bootloader/kernel/
10MB
N/A
uramdisk images
User
VFAT. Mount as/
Media file storage
Defined
sdcards
EXT4. Mount as/
Android system bin/
≥ 200MB
system (with read
libs (system.img)
only)
EXT4. Mount as/
Android data
data
(e.g. installed app)
EXT4. Mount as/
> 10MB
Android cache
cache
Root file system
EXT4. Mount as/
> 20MB
for recovery mode
in recovery mode
(recovery.img)
Note:
/dev/sdxN, the x is the disk index from 'a' to 'z', that may be different from each
Linux PC.
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