Difference between revisions of "Android File System"

Revision as of 20:22, 4 July 2012

Microsoft Windows users are familiar with the terms FAT32, or NTFS, which refers to types of file systems. Android devices are developed on Linux, which is based on UNIX. Linux users are familiar with good old ext2 file system. Well, your Android device may use an updated Linux file system, such as ext4, or a proprietary file system by a manufacturer, depending on who made the device and and what has been done to it by the user.

Samsung Galaxy S phones use the Samsung RFS proprietary file system while the Samsung Nexus S with Android 2.3 uses the Linux Ext4 file system. The new open standard Ext4 file system seems to be the popular standard. Android phones use the Linux kernel, and as many linux users know, linux can support a large number of operating systems.

The SDCard may be formatted ext3 or YAFFS (citation needed - verify example)

SDCard

The mounted SDCard is a storage device mounted to the file system in the typical Linux fashion. On the file system root the /sdcard is a symbolic link to /mnt/sdcard. /mnt/sdcard is where the SD card is actually mounted, but the same files can also be accessed in /sdcard.

• /mnt/sdcard --- Your removable SD card data is stored here.

The Samsung Galaxy Tab 2 actually has two SDCard mounts, one for a built-in internal SDCard which is different than the device memory on a typical Android phone, and the second is the removable SDCard.

• /mnt/extSdCard --- On the Samsung Galaxy 2 tablet this is the removable SD card.

Every Android-compatible device supports a shared "external storage" that you can use to save files. This can be a removable storage media (such as an SD card) or an internal (non-removable) storage. Files saved to the external storage are world-readable and can be modified by the user when they enable USB mass storage to transfer files on a computer.

DCIM

• typically /sdcard/DCIM or /DCIM

Android uses the DCF (Design rule for Camera File system) specification. All digital cameras contain a DCIM (Digital Camera IMages) folder in their root directory. Inside this will be multiple folders named nnnABCDE, where nnn is a unique directory number between 100-999 and ABCDE is a five-character alphanumeric string often (but not required to be) related to the camera manufacturer. Image files stored within these folders will have a file name in the format ABCDnnnn, where ABCD is a four-character string (often DSC_ or IMG_) and nnnn is a unique sequential index number.

External Storage Public Directory

Some people are using a "media" intermediary directory between the standard public directory and the storage root. See below

• /sdcard/media/alarms OR /sdcard/Alarms
• /sdcard/media/notifications OR /sdcard/notifications
• /sdcard/media/ringtones OR /sdcard/ringtones
• /sdcard/media/ui OR /sdcard/ui

Warning: This may be incorrect. Below is from the Android developer's reference explaining the correct way.

Android developer's reference explains that there are certain public storage directories that are not specifically tied to a specific program. So if a program is uninstalled, it should never remove data from one of these standard public storage directories. These directories lay at the root of the external storage, such as Music/, Pictures/, Ringtones/, and others.

• Music/ - Media scanner classifies all media found here as user music.
• Podcasts/ - Media scanner classifies all media found here as a podcast.
• Ringtones/ - Media scanner classifies all media found here as a ringtone.
• Alarms/ - Media scanner classifies all media found here as an alarm sound.
• Notifications/ - Media scanner classifies all media found here as a notification sound.
• Pictures/ - All photos (excluding those taken with the camera).
• Movies/ - All movies (excluding those taken with the camcorder).
• Download/ - Miscellaneous downloads.

So an example would be /mnt/sdcard/Pictures which is made up of the first part, /mnt/sdcard (or just /sdcard) that being the root of the sdcard and then one of the directories above.

Keywords: Android Tablet PC Samsung Galaxy Tab Two 2 FS File System Root Linux