I want to change the init.rc file of an android pad. But after I change it and reboot the system, the original init.rc comes back.
How can I make the change to the init.rc persistently without rebuild the system (since I don't have the source code of the system)? Or is there any way to work around?
Unpack the uramdisk using following command in host PC(Linux)
mkdir /tmp/initrc cd /tmp/initrd
sudo mount /dev/sdb1 /mnt
sdb1 is partion where uramdisk/uInitrd resides.
dd bs=1 skip=64 if=/mnt/uInitrd of=initrd.gz
gunzip initrd.gz
At this point running the command file initrd should show:
mkdir fs
cd fs
cpio -id < ../initrd
Make changes to init.rc
Pack uramdisk using following commands:
find ./ | cpio -H newc -o > ../newinitrd
cd ..
gzip newinitrd
mkimage -A arm -O linux -C gzip -T ramdisk -n "My Android Ramdisk Image" -d newinitrd.gz uInitrd-new
A number of Android devices include code to prevent root modifications to the system files. The way this is done is by using the recovery partition. On reboot, they basically restore the system partition using the recovery image. If your system is doing that then you cannot make persistent changes - the best you could do would be to hook up something to run after reboot to re-apply your change. In CyanogenMod they had hooks in the init.rc to run sdcard scripts if found. Perhaps you can create an app or widget to then launch a script to make the mods required using a setuid root script from the data partition. Without building your own ROM you are quite restricted in this area.
Possibly you could fetch the recovery image and try unpacking that, making your changes and repacking and flashing it. But make sure you can recover with fastboot before you try this.
Try this site:
http://bootloader.wikidot.com/linux:boot:android
Read the section at the bottom:
•The Android boot image: boot.img
◦Unpack, re-pack boot image: http://android-dls.com/wiki/index.php?title=HOWTO:_Unpack%2C_Edit%2C_and_Re-Pack_Boot_Images#Background
When an android system boots, uboot unpacks a special compressed ball of files in your boot partition called 'uRamdisk' to RAM, and defines those files to comprise the root directory of the system. uRamdisk normally contains a bunch of directories (system, data, media, etc.) that serve as mountpoints for partitions that contain the files that go in them, but also has some very basic files vital to your system, including the init binary and startup scripts like init.rc.
when you edit the init.rc, you've actually just edited the unpackaged copy of init.rc that resides in your RAM. To really change it then, you have to copy your uRamdisk, extract it, edit the init.rc from there, repackage uRamdisk and then replace the new one with the old one in /boot.
Try looking up the 'xuramdisk' and 'mkuramdisk' scripts, these make the process very simple.
Your root partition (where /init.rc lives) is a ramdisk which is unpacked from an initrd file and mounted every time your device boots. Any changes you make are to the ramdisk only, and will be lost on the next reboot.
If you can get the initrd file, you can mount it on your Linux host system, modify the files there, unmount it, and write it back to your Android.
The initrd file exists in its own partition on the device. If you can figure out which partition it is, you can grab it from the device onto your host, mount it, modify it, and write it back to the device. This is what tripler was talking about above.
In general, modifying boot.img is something that only system developers do. If you're building the entire Android system, you'll have access to the necessary source code. My workflow for this looks like this:
# Modify init.rc
m -j8 bootimage_signed
adb reboot bootloader
fastboot flash boot $OUT/boot.img
fastboot reboot
I don't know if you are still trying to do this but without knowing your exact device nobody can give you an exact answer.
Try taking a dd image of all your internal partitions and use some scripts like those included with android kitchen on xda forums. Your recovery and boot partitions will both have a ram disk but odds are you want to modify the init.rc in the boot.img not recovery, unless you only want the changes present in recovery mode.
The unyaffs thing doesn't apply to all devices and most devices have different partition layouts so you have to figure out which is boot and what type of fs it is. Maybe if you give your device specs you can get a better answer.
Please note that it may be easier for you to use an app like Scripter to run a script at boot time than modify this file.
Before following #tripler's instructions above you need a file called boot.img which can be extracted by (run on rooted Android device, untested without root):
dd if=/dev/block/platform/<someplatform>/by-name/boot of=/sdcard/boot.img
Then connect your Android to your computer and copy the boot.img file from there.
Script:
http://linuxclues.blogspot.ca/2012/11/split-bootimg-python-android.html
Here is a modified, easier to see version of tripler's instructions (assuming boot.img is in tmp):
cd /tmp
mkdir fs
# Now use the linked script above to split the boot.img file into ramdisk.gz and kernel
python split_boot_img.py -i boot.img -o parts
cd fs
gunzip -c ../parts/ramdisk.gz | cpio -id
# make changes to init.rc
At that point you will have to rebuild the boot.img back together before reflashing, which will be device-specific. Can't help you with that, sorry!
You have to edit/change the init.rc before building your Android pad file system. This is the preferred way, and always works.
Related
If I change a .mk or a .xml file in the android source code, how do I send this updated file to the device? Do I first rebuild the source tree? Or is building not necessary? After building/not-building, do I use adb push or adb sync or do I have to reflash the device?
No you can't just push the these files as these files are merged in the img file like boot.img ,system.img etc. so you need to find out that in which img file these .xml files are added. Then you just need to make that img file like
make bootimage -j4
and flash the image to the device
In case you did't figure out then you need to rebuild the source tree.
Yes building is absolutely necessary. See https://source.android.com/setup/build/building for more complete information but here are some quick notes:
If using mm or related commands you can usually follow it up with adb remount (needed just once per boot) and then: adb sync, adb shell stop, adb shell start.
If you built the entire tree via a command such as lunch aosp_xyzdevice-eng then you should probably use fastboot or other raw flashing tool provided by your SOC to flash the entire system image (and possibly boot or other images) to the device.
I am trying to modify the init.rc file on Nexus 7 device which is rooted.
I want to insmod a simple hello world module before my /userdata/ partition is mounted.
Things I have tried:
Extracted the boot.img from the device, extracted the ramdisk, made changes to the init.rc (which do not work), recreated the boot.img (using mkbootimg tool) and then flashed it on the device again
I have placed my hello.ko compiled for the kernel at 2 places: one is the current directory in which init.rc is placed, so that I can do something like insmod hello.ko and it will find it. Secondly, I created /lib/modules/ directory and placed it inside that
In my init.rc I have placed the insmod /lib/modules/hello.ko right after on_boot.
I have also changed the init.flo.rc and placed the insmod before and after ./mount_all which mounts the file system.
However, I do not see my module loading at all.
The permissions set were 0644 ( I tried with 0777 too)
I created init.d inside /etc/folder and placed a loadmodule.sh which does an insmod /lib/modules/hello.ko and that module loads but once the boot process has completed.
I ideally want to do it right before mounting the /userdata/ partition.
Can someone help me with this?
My device is a Nexus 7, with flo_kernel and rooted, busybox installed, etc.
The root filesystem on an Android device is "read-only", insofar that you cannot hang any files off the root tree and expect it to stay around. This is the same reason that you needed to extract the ramdisk and re-pack its contents in order to persist an init.rc change; any files you want to also locate at / must be packed into the ramdisk as well. Android extracts root from the ramdisk on every boot.
A more conventional location for that file would be on the system partition, say in /system/lib
I've selected several of the trace tags and when I run the trace (from DDMS) I get the following output:
Unexpected error while collecting system trace. Unable to find trace start marker 'TRACE:':
error opening /sys/kernel/debug/tracing/options/overwrite:
No such file or directory (2)
error openi(cuts off the error here)
indeed there is no debug file in the kernel directory, but which mechanism will generate the necessary path?
It looks like your cellphone is running a boot(kernel) image that does not support systrace.
"error opening /sys/kernel/debug/tracing/options/overwrite: No such file or directory (2)"
This error message means adb daemon (the adb module running on device side) could not find /sys/kernel/debug/tracing/options/overwrite on your device's file system. systrace works over adb and communicates with kernel though sysfs nodes under /sys/kernel/debug/tracing. If these nodes are not exposed on you phone for whatever reason, systrace just will not work.
So you should first get a shell on your device using:
adb shell
Then browse to confirm if /sys exists at all and if /sys/kernel/debug/tracing exists.
If they are there which is extremely unlikely, you have to debug systrace.py to figure out how come systrace think the nodes were not there. Otherwise, you need to flash a different boot image which has systrace support, because sysfs is controlled by kernel(mostly by configurations at compile time) and init.rc , both of which are part of boot image.
Flashing a different boot image might involve unlocking/rooting the device. You probably have to go to fan sites like xdadeveloper for information and image. Another option is to download the source of kernel for your device, compile kernel and make the boot image yourself. Linux is under GPL thus manufacturer of your device is obligated to release the source code of the specialized kernel they use.
-NAM
http://www.willpromo.com
You may need to slightly modify the kernel image(boot.img). The following work find for me, just for your reference.
open terminal and enter: $adb shell
(1) $su (2) $mount -t debugfs none /sys/kernel/debug. Now you should be able to see many directories under /sys/kernel/debug/. (You may cd into /sys/kernel/debug to confirm this)
Enter: $dd if=/dev/block/platform/msm_sdcc.1/by-name/boot of=/sdcard/boot.img to generate the boot.img kernel image from your device.
Use AndroidImageKitchen to unpack the boot.img and find the default.prop within Ramdisk folder. Then change ro.debuggable=0 to ro.debuggable=1. Repack the boot.img and flash boot it to your device.
Once the device boot, under terminal, enter: $adb root and message like: $restarting adbd as root may pop up. Disconnect the USB and connect again.
cd to the systrace folder, e.g. ~/androidSDK/platform-tools/systrace and use:
python systrace.py --time=10 -o mynewtrace.html sched gfx view wm
Now you may able to generate your own systrace files.
I need to patch a file into the system.img file used by the Android emulator, specifically I want to add an ARM binary to the /system/bin directory.
I have this binary pre-compiled and it works in my emulator perfectly, but I can't simply remount system.img as rw and adb push it because the change is non-persistent across reboots. I tried this on a copy of system.img and passing it to the emulator with -system but that was non-persistent to sadly.
In the ideal world I want to modify the "make sdk" process so that the sdk build process automatically includes my binary when it produces system.img. Can this be done?
If this isn't possible, is there anyway of patching it into the image manually?
Thanks a lot.
I was interested in permanently modifying the /system folder and tried unpacking the system.img file which went ok, but I failed to create a new img that the emulator was happy with (using the mkyaffs2 and unyaffs2 tools to extract and create a new system.img).
Instead I found a much easier solution:
Remove everything from the /data/ directory (except lost+found)
Copy the contents of /system into your /data folder
Make your desired changes to /data/
Kill the emulator
You now move your ~/.android/avd/MYANDROID.avd/userdata-qemu.img to ~/system.img (or wherever)
and startup your emulator with your new system image:
emulator -debug all -show-kernel -verbose -avd MYANDROID -no-boot-anim \
-gpu on -partition-size 800 -system [path to your new system.img]
The /data folder is where the userdata-qemu.img file gets mounted.
It gets created the first time the emulator is run and will get recreated if you delete it.
(though your installed apps will disappear).
BY populating it with the contents of the /system folder and then making your desired modifications you have created a replacement for the system.img file.
system.img replace with original one so you need give patches whenever your emulator boots check logcat & then using ADB push you manually push the patches.
I have my Nexus One connected with the USB.
When I visit the File Explorer of the DDMS, if I click on the "data" folder the little plus near the name "data" disappear for 2-6 seconds and then reappear but the contenct of the folder "data" is not showed!
Here some other information:
the folder data has permissions drwxrwx--x
the OS of my PC is Windows XP
Eclipse v. 3.5.2
Android SDK 1.6
If the adbd daemon is running as root, you can browse /data using adb-based tools such as the DDMS file explorer or the adb shell.
If it's not, you can access a few files under /data and its children directly by their full path names, but you cannot browse (or 'cd' to) most of the folders, including /data itself.
"rooting" as an unofficial process means varying things and produces varying results - ie, adbd may or may not run as root.
If ro.secure is set to 0 in the startup scripts such as /init.rc, adbd will run as root, but that may not be a good idea on a user device. It is set to 0 on the emulator, and that's why you can browse /data there.
Finally, note that /init.rc is usually contained in a ramdisk image packed onto the kernel - you can't really edit it on the phone but would have to modify the image offline, re-attach it to the kernel, and re-flash them. Though if you have some sort of working 'su' hack you may be able to change the property temporarily and restart adbd.
In this link (http://denniskubes.com/2012/09/25/read-android-data-folder-without-rooting/) Dennis Kubes shows a method for accessing your application's data folder without root access.
Turns out there is a simple solution, the run-as command.
run-as com.your.package ls -l /data/data/com.your.package
run-as com.your.package rm /data/data/com.your.package/databases/mydatabase.db
That will allow you to run commands as your app. You can also use run-as in interactive mode.
run-as com.your.package
shell#android:/data/data/com.your.package $ ls
cache
databases
lib
shared_prefs
rm databases/mydatabase.db
Interactive mode will drop you into the data folder for your app. You can navigate from there.
I don't think anyone really understands this question. Giorgio can use the DDMS File Explorer to browse the ./data folder on his phone. Pentium10 talks about needing root access on the phone.
Well I a retail Nexus One and a developer Nexus. I have always been able to use DDMS File Explorer to browse the ./data folder on my developer phone but not my retail phone. So I rooting my retail phone would help. I didn't.
So the bottom line is there is something different about the retail and developer phones. Until more research is done you won't be able to browse the data folder on your phone.
Hope this helps.