Develop Reference

How to unzip, unpack and convert android rootfs to ext4

Android rootfs is compressed and split into:
super.raw.00.gz, super.raw.01.gz, super.raw.03.gz, super.raw.04.gz
How to unzip, combine, unpack them to ext4 files that can be mounted ?

Steps are:
Unzip each of the multi-zip files:
gzip -d super.raw.00.gz
gzip -d super.raw.01.gz
gzip -d super.raw.02.gz
gzip -d super.raw.03.gz
Concatenate them to a single file:
cat super.raw.00 super.raw.01 super.raw.02 super.raw.03 > super.raw
Unpack the super image using lpunpack tool. Download link.
./lpunpack super.raw
Mount the image- For eg: system_a
mkdir mount_system
sudo mount -t ext4 -o loop system_a.img mount_system

File not found in /data/media/0, but found in /storage/emulated/0

I use the smartphone emulator in Android Studio for a Nexus 4, API 23.
I took a picture through its camera, and I can check that the file is present at this different paths through the Android Device Monitor:
/data/media/0/DCIM/Camera/IMG_20160408_143726.jpg (rw-rw-r)
/storage/emulated/0/DCIM/Camera/IMG_20160408_143726.jpg (rw-rw)
Nevertheless, in my Activity I got different behaviors when I try to read the file:
new File("/data/media/0/DCIM/Camera/IMG_20160408_143726.jpg");
// isFile at false, canRead at false, length at 0
new File("/storage/emulated/0/DCIM/Camera/IMG_20160408_143726.jpg");
// isFile at true, canRead at true, length with a real value
Why is it so?

it depends on contructor, use this method to get the sdcard path instead, that will find the correct path for all devices
new File(Environment.getExternalStorageDirectory().getAbsolutePath() + "/DCIM/Camera/IMG_20160408_143726.jpg")

You probably would like to grant your app root permission so as to let it work properly. Take a look at this example:
u0_a1#android:/ $ toolbox ls -l /storage/emulated/0/UPDATE*
-rw-rw---- root sdcard_r 4997896 2016-09-08 20:08 UPDATE-SuperSU-v2.78.zip
u0_a1#android:/ $ toolbox ls -l /data/media/0/UPDATE*
/data/media/0/*: Permission denied
1|u0_a1#android:/ $ su
root#android:/ # toolbox ls -l /data/media/0/UPDATE*
-rw-rw-r-- media_rw media_rw 4997896 2016-09-08 20:08 UPDATE-SuperSU-v2.78.zip

Read only file system android (is /mnt not /system)

Android device, I want to touch a file or dir in /mnt, it say "Read only file system", I don't know how to do. i try fix it with that fix /system, but it no work.
root#android:/ # ls -l
.....
drwxrwxr-x root system 2011-01-01 11:33 mnt
.....
root#android:/ #
root#android:/ # mkdir /mnt/test
mkdir failed for /mnt/test, Read-only file system
255|root#android:/ #
root#android:/ # mount -o remount,rw /mnt
Usage: mount [-r] [-w] [-o options] [-t type] device directory
1|root#android:/ #
can't fix it as /system.
how can i do it?
root#android:/ # id
uid=0(root) gid=0(root)
root#android:/ #
But i can make directory in /mnt/xxx/, like this:
root#android:/ # mkdir /mnt/usb_storage/test
root#android:/ # ls /mnt/usb_storage/test/
root#android:/ # ls /mnt/usb_storage/
test
root#android:/ #
And
i fond difference between /mnt and /mnt/usb_storage in init.rc
look /mnt:
# create mountpoints
mkdir /mnt 0775 root system
look /mnt/usb_storage:
# Directory for multi usb storage
mkdir /mnt/usb_storage 0700 root system
mount tmpfs tmpfs /mnt/usb_storage mode=0755 gid=1000
Yes!I fix it!
create mountpoints
mkdir /mnt 0775 root system
add mount tmpfs tmpfs /mnt/ mode=0755 gid=1000
now i can touch file or make directory in /mnt
root#android:/mnt # mkdir /mnt/test
root#android:/mnt # ls -l /mnt/
....
drwxrwxrwx root root 2011-01-01 11:04 test
drwxrwxrwt root system 2011-01-01 11:00 usb_storage
root#android:/mnt #
Resolved
ramdisk rootfs is read only.
mount -o remount,rw /

you should have to add certain permission into your manifest file..
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
and for more see the following which near to what you looking for
Can't create file in sd-card

how to build a dir and file at /system file using code

my app have root right ,i want to using code to build a dir or file at /system or other dir of device.
i know common java build file as:
File file = new File(destFileName);
if (file.exists()) {
return false;
}
if i can build dir at system like the above code?if i need use su command before build file dir as
Process p = null;
p = Runtime.getRuntime().exec("su");
edit: i have read Create a file in /system directory but i cannot using code write :
" hint: use the "adb shell" and check if the upper steps can lead to success (su && remount -o remount,rw /system && touch /system/test)"

You need to get /system be mounted for write. By default it is read-only. You can use command like mount -o remount,rw /system
You can create dir using mkdir command
You can change the owner user by chown command
After that you can use java code as ususal.

Android File.listFiles does not show all the files inside the directory

I am using Android Emulator 2.2 version to develop a small application. I am supposed to list all the image files(jpg) files under a directory. I copied the files to "/data" through ADB puash command.
Example : /data/1.jpg
Now I create a File object with the directory path as input and call listFiles api.
File dir = new File(dirPath);
File[] filelist = dir.listFiles();
But the fileList does not contain the image file(1.jpg).
But strangely, If I create a ImageView with hardcoded path "/data/1.jpg", I could see the image getting drawn.
Can some one help me.... where could be the problem
Thanks,
Kowndinya
public int PopulateList(final String dirPath)
{
m_CurrentDirectory = new File(dirPath);
_namelist.clear();
_pathlist.clear();
File[] fileList = m_CurrentDirectory.listFiles(imFilter);
if (fileList != null)
{
for ( int i = 0;i<fileList.length;i++)
{
_namelist.addElement(fileList[i].getName());
_pathlist.addElement(fileList[i].getAbsolutePath());
}
}
notifyDataSetChanged();
return 0;
}
imFilter is an filenamefilter that accepts only files with jpg extension. But if I put break point in the imFilter code, break point does not event hit.
Output of adb shell ls -l /data:
------------------------------------
drwxrwx--t system misc 2010-08-05 15:32 misc
drwxrwx--x shell shell 2010-08-05 15:32 local
drwxrwx--x system system 2010-08-05 15:32 app-private
drwx------ system system 2010-08-05 15:34 backup
drwx------ root root 2010-08-05 15:34 property
drwxrwx--x system system 2010-08-05 15:35 data
-rw-rw-rw- root root 75752 2010-03-30 12:26 zona_ind_012.jpg
drwxrwx--x system system 2010-08-05 16:16 app
drwxr-x--- root log 2010-08-05 15:32 dontpanic
drwxrwx--x system system 2010-08-05 16:25 dalvik-cache
drwxrwxr-x system system 2010-08-05 17:16 system
drwxrwx--- root root 2010-08-05 15:32 lost+found

I explore that code, and see, trouble is in permission. As you can see below, you can't read that dir.Find another dir to collect your files.
**Can read dir:**
/dev =true
/root =false
/data =false
/default.prop =true
/init =false
/init.rc =false
/proc =true
/sbin =false
/sys =true
/system =true
/etc =true
/d =false
/mnt =true
/acct =true
/sdcard =true
/cache =false
/config =false
and that you can see from "ls -l" command.
explain what does mean