System. IMG, userdata. IMG, and ramdisk. IMG in Android emulator

In Android emulatorSystem. IMG, userdata. IMG, and ramdisk. img

1. Structure of the android File System
After the android source code is compiled, the system. IMG, ramdisk. IMG, and userdata. IMG image files are obtained. Ramdisk. IMG is the file system of emulator. IMG includes the main packages, libraries, and other files, userdata. IMG includes user data. After loading these three image files, emulator loads system and userdata to the system and userdata directories in the ramdisk file system. Therefore, we can copy all the files in ramdisk. IMG and extract system. IMG and userdata. IMG
The system and userdata directories in the ramdisk file system.

2. Detach the android File System
system. IMG, ramdisk. IMG, userdata. the IMG image file is packaged with cpio and compressed with gzip. You can run the file command to verify that:
file ramdisk. IMG, output:
ramdisk. IMG: gzip compressed data, from UNIX, last modified: We D mar 18 17:16:10 2009
after the android source code is compiled, the system and userdata folders are generated in addition to system. IMG and userdata. IMG, so you do not need to decompress them. After the android source code is compiled, the root folder is also generated. In fact, the files under root and ramdisk. the files in IMG are the same, but here we will introduce how to use ramdisk. decompress IMG:
unzip, and run the
gunzip ramdisk.img.gz
command to create a folder, enter ramdisk and enter the command
cpio-I-f .. /ramdisk. IMG
now, you can see and operate the content in ramdisk.
copy the files in system and userdata generated after compiling the android source code to ramdisk/system and ramdisk/userdata. In this way, a file system is obtained.

3. Mount the android File System Using a Network File System
Therefore, we need to create the/nfsroot directory, create the/nfsroot/androidfs directory, change the android File System to androidfs, and link to/nfsroot/androidfs.

4. Android kernel boot file system
After mounting the android kernel/nfsroot/androidfs, initialize and load the system library according to init. RC and init. Goldfish. RC,ProgramWait until the boot is complete. The init. RC Script includes many file system initialization and loading processes. The main work of init. RC is:
1) set some environment variables
2) create directories such as system, sdcard, data, and Cache
3) mount some file systems to some directories, for example, Mount tmpfs/sqlite_stmt_journals
4) set user groups and permissions for some files
5) set some thread parameters
6) set the TCP cache size

From: http://pccp.me/archives/39.html