Android File System Hierarchy

Original source from : http://anantshri.info/andro/file_system.html

/  ▼: Base file system : Generally recreated everytime using ramdisk content

•  cache : Cache Folder : Used as scratch pad by OS place dex optimized dalvik bitecode
• ▼data  :Contains USER Data Stored as a separate partition in mtdblocks mounted at bootup
•   anr
•   idd
•   system
•   radio
•   property
•   app : Application : User installed
• ▼data  Downloaded, updated and manually installed apps
•    folder for each app named as package name.
•   local
•   dalivk-cache
•  default.prop : Default Property settings, Values restored from this file on every restart
• ▼dev : Device file system pointers
•  tty 1 - 63
•  null
•  zero
• ▼block   Block Devices
• loop 0-7 : Loop back devices
• mtdblock 0 - 6-8 : MTD BLOCKS : Device internal memory
• mmcblk0 : SDCARD Block Device
• etc -> /system/etc : Soft link to /system/etc Directory
• hw_config.sh
• init : INIT executable, this is also the place where device nodes are created by listening to uevents
•  init.rc : Initial Configuration file : decompressed from ramdisk
• logo.rle : Boot Time Logo
•  ▼proc
• last_kmsg : Previous Sessions Kernel message log
• partitions
• diskstats
• kmsg : Kernel Message log simmilar to dmesg in linux
• cpuinfo : CPU information simmillar to linux
• config.gz : Copy of .config used to compile kernel (optional)
• root
• ▼sbin        Part of Ramdisk Content : This contains various executables required for Bootup
•  adbd        ADB Daemon executable: Responsible for adb shell
•  ▼sys
•  fs
•  devices
•  dev
•  bus
•  class
•  firmware
•  kernel
•  power
•  module
•  block
• ▼system : Main OS System. Stored as a separate partition in mtdblocks mounted at bootup (read-only)
• app  : System Apps : Pre installed : Android Specific, Vendor and Carrier Provided Application set. These applications can't be changed without rooting device(till version 4.0 of android)
•  ▼bin : Binary Executables required for operation
• installd  : Native package management daemon
• keystore : keystore for android
• netd : Communication daemon
• rild : modem communication
• system_server : Key server in android performing most critical task and providing most services. Combination of cpp and java code. The system server communicates with vold/rild etc
• vold :Volume manager that listens to kernel netlink events and mounts media
• 
  
   build.prop : File containing Configuration variables used to define various operational parameters
• etc : Configuration Files for Whole Android System
• framework : Framework : jar Files which provision the interaction between applications and hardware
• fonts : Fonts used in display
• media : Contains Media files ringtone/alarms etc
• xbin : Excutable Files generally this holds special executables like busybox or toolbox
•  sdcard : SDCARD :removable sdcard directory
•  ▼mnt
•  sdcard -> /sdcard : Link too /sdcard