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HOWTO: Unpack, Edit, and Repack Boot Images

Several people have already figured out the details on their own, but I have gotten requests to do a more comprehensive tutorial on how the boot and recovery images are structured, and how you can edit them.
Background
Your phone has several devices which hold different parts of the filesystem:
Code:
#cat /proc/mtd
dev: size erasesize name
mtd0: 00040000 00020000 "misc"
mtd1: 00500000 00020000 "recovery"
mtd2: 00280000 00020000 "boot"
mtd3: 04380000 00020000 "system"
mtd4: 04380000 00020000 "cache"
mtd5: 04ac0000 00020000 "userdata"
In this tutorial, we will deal with "recovery" and "boot". The "boot" device holds the files that are automatically loaded onto the root of your filesystem every time you boot (details below).
"system" holds everything that gets mounted in your system/ directory, and userdata/ is everything that shows up in data/ (this is all the apps you've installed, your preferences, etc).
The recovery and boot partitions are at /dev/mtd/mtd1 and /dev/mtd/mtd2, and before you do anything else you should back these up (note: this may not be the best way of doing this because it may not deal properly with bad blocks etc, but it's all we've got until somebody comes up with a better method, and besides you will probably be restoring from update.zip anyway):
Code:
# cat /dev/mtd/mtd1 > /sdcard/mtd1.img
# cat /dev/mtd/mtd2 > /sdcard/mtd2.img
The other thing you should do is put your favorite update.zip file into the root directory of your sd card so that if you screw up your boot partition you can boot into recovery mode and re-apply the update. You probably want one of the pre-rooted recovery images found elsewhere on the forums.
There is also another important file you should know about. In /system/recovery.img there is a full copy of everything that is loaded on mtd1. This file is automatically flashed onto mtd1 every time you shut down. That means two things: 1. Any changes you make directly to /dev/mtd/mtd1 get blown away on reboot and 2. If you want to change /dev/mtd/mtd1 you're probably better off just sticking the image in /system/recovery.img and rebooting. When creating your own custom update.zip files (especially when adapting the stock images), you can get tripped up if you forget to replace /system/recovery.img and it ends up overwriting /dev/mtd/mtd1 unbeknownst to you. Watch out.
Structure of boot and recovery images
The boot and recovery images are not proper filesystems. Instead, they are a custom android format consisting of a 2k header, followed by a gzipped kernel, followed by a ramdisk, followed by a second stage loader (optional, we have not seen these in the wild yet). This structure is outlined in mkbootimg.h:
Code:
+-----------------+
| boot header | 1 page
+-----------------+
| kernel | n pages
+-----------------+
| ramdisk | m pages
+-----------------+
| second stage | o pages
+-----------------+
n = (kernel_size + page_size - 1) / page_size
m = (ramdisk_size + page_size - 1) / page_size
o = (second_size + page_size - 1) / page_size
0. all entities are page_size aligned in flash
1. kernel and ramdisk are required (size != 0)
2. second is optional (second_size == 0 -> no second)
A ramdisk is basically a small filesystem containing the core files needed to initialize the system. It includes the critical init process, as well as init.rc, which is where you can set many system-wide properties. If you really want to know more about it, here is the documentation. Here's a list of files on a typical ramdisk:
Code:
./init.trout.rc
./default.prop
./proc
./dev
./init.rc
./init
./sys
./init.goldfish.rc
./sbin
./sbin/adbd
./system
./data
The recovery image typically has a few extra files, which constitute the recovery binary and supporting files (the application that gets run if you hold down home+power when rebooting). These files are:
Code:
./res
./res/images
./res/images/progress_bar_empty_left_round.bmp
./res/images/icon_firmware_install.bmp
./res/images/indeterminate3.bmp
./res/images/progress_bar_fill.bmp
./res/images/progress_bar_left_round.bmp
./res/images/icon_error.bmp
./res/images/indeterminate1.bmp
./res/images/progress_bar_empty_right_round.bmp
./res/images/icon_firmware_error.bmp
./res/images/progress_bar_right_round.bmp
./res/images/indeterminate4.bmp
./res/images/indeterminate5.bmp
./res/images/indeterminate6.bmp
./res/images/progress_bar_empty.bmp
./res/images/indeterminate2.bmp
./res/images/icon_unpacking.bmp
./res/images/icon_installing.bmp
./sbin/recovery
Unpacking, Editing, and Re-Packing the images
Note: below I give you the details for unpacking and repacking manually, but I have attached two perl scripts that do most of this for you
If you are good with a hex editor, you can open up any of these images and strip off the first 2k of data. Then, look for a bunch of zeroes followed by the hex 1F 8B (which is the magic number of a gzip file). Copy everything from the first line of the file, through the zeroes, and stopping at the 1F 8B. That is the kernel. Everything from the 1F 8B through the end is the ramdisk. You could save each of these files separately. In order to see the contents of the ramdisk, you need to un-gzip it and then un-cpio it. You could use a command like this (ideally after creating a new directory and cd'ing into it):
Code:
gunzip -c ../your-ramdisk-file | cpio -i
That will place all of the files from the ramdisk in your working directory. You can now edit them.
In order to re-create the ramdisk, you need to re-cpio them and re-gzip those files, with a command like the following (remember, cpio will include everything in the current working directory, so you probably want to remove any other cruft you might have in there):
Code:
find . | cpio -o -H newc | gzip > ../newramdisk.cpio.gz
The final step is to combine the kernel and your new ramdisk into the full image, using the mkbootimg program (which you should download and compile from the git repository):
Code:
mkbootimg --cmdline 'no_console_suspend=1 console=null' --kernel your-kernel-file --ramdisk newramdisk.cpio.gz -o mynewimage.img
Now, there's a lot of hassle in pulling apart files in hex editors and remembering all of these commands, so I wrote unpack and repack perl scripts for you (attached). Hooray.
Flashing your new image back onto the phone
You will probably only ever be flashing boot images directly to the phone, given the fact that /system/recovery.img automatically flashes the recovery device for you (as noted above). If you have created a new recovery image, just stick it in /system/recovery.img and reboot. If you are flashing a boot image, stick it on your phone via adb (a tool included in the Android SDK):
Code:
adb push ./mynewimage.img /sdcard
Then, open a shell to your phone via 'adb shell', get root, and do the following two commands to flash your new boot image:
Code:
# cat /dev/zero >> /dev/mtd/mtd2
write: No space left on device [this is ok, you can ignore]
# flash_image boot /sdcard/mynewimage.img
Reboot.
If your phone starts all the way up, congratulations. If not, you did something wrong and you'll need to boot into recovery mode and apply your update.zip file (reboot while holding down home+power, when you get the recovery screen press alt+L and then alt+S).
Something fun to do with your new found power
If you place a file titled initlogo.rle in the root directory of your boot image, the phone will display this image upon boot (after the "G1" image and before the Android animation). In order to create this file, you need to create a 320x480 image in Photoshop or Gimp and save it as a "raw image" file. You then need to compress that image with the program to565. More details on that here.
This is not the same thing as applying an update.zip
You will see other places on the forums that describe how to create customized update.zip files, as well as update.zip files that people are sharing. For example, there is a recent update.zip which is a modified version of rc30 (with the anti-root aspects disabled). The update.zip files include new boot images, recovery images, and typically replacements for the entire system/ directory as well as other updates. If you are creating a custom boot or recovery image, it is typically a good idea to start with the image distributed with the most recent update you have applied (flashing an image from an older release could have unintended consequences).
Questions?

hooray! you're awesome

Where does boot.img flash? What is the corresponding part of the system?

Dimath said:
Where does boot.img flash? What is the corresponding part of the system?
Click to expand...
Click to collapse
I'm not sure what exactly you mean, but when you do flash_image boot imagefile.img it will write imagefile.img to /dev/mtd/mtd2, which is where your phone looks for the boot files. Did that answer your question?

For your command...
Code:
cat /dev/zero >> /dev/mtd/mtd2
Do you mean
Code:
cat /dev/zero > /dev/mtd/mtd2
?
The idea being that you erase flash in the version with one '>', whereas you... append to the end of a device in the version with two '>'s? I can see the utility of erasing flash with one '>' but appending seems... odd. Am I missing something?

Is this any different than using the Dalvik Debug Monitor (DDMS) file manager found the the Android SDK? I'm able to push, pull, and delete files on my G1 with no problem.

Would this be the only way to rebuild a system app (i.e. Settings.apk) with more debug (Log. to extract via adb logcat over usb), then rebuild the entire system.img, then flash into the G1?

eckzow said:
For your command...
Code:
cat /dev/zero >> /dev/mtd/mtd2
Do you mean
Code:
cat /dev/zero > /dev/mtd/mtd2
?
The idea being that you erase flash in the version with one '>', whereas you... append to the end of a device in the version with two '>'s? I can see the utility of erasing flash with one '>' but appending seems... odd. Am I missing something?
Click to expand...
Click to collapse
I think you're right. I copied that from somebody else's instructions and it certainly seems to make more sense with one '>'. Anybody know for sure?
In any event, this is unnecessary in most cases because flash_image should overwrite the whole thing. The only exception is when you have an identical header on your image to the one that is already on the device. This shouldn't happen in my instructions (mkbootimg creates a header that includes the build timestamp) but I kept the instruction there just for good measure.

andonnguyen said:
Is this any different than using the Dalvik Debug Monitor (DDMS) file manager found the the Android SDK? I'm able to push, pull, and delete files on my G1 with no problem.
Click to expand...
Click to collapse
The adb push command I gave is no different, but you would still have to unpack/repack and flash_image according to my instructions.

I've tried these instructions on RC30 1.3. Basically I extracted, unpacked, and repacked, just to see if it would work. The resultant file is too large; it fails when you run flash_image.

I'm trying to modify my boot image of my ADP1 using the perl scripts, but I receive the following warning while decompressing the ramdisk:
Code:
$ unpack-bootimg.pl mtd2.img
kernel written to mtd2.img-kernel.gz
ramdisk written to mtd2.img-ramdisk.cpio.gz
removed old directory mtd2.img-ramdisk
[B]gzip: ../mtd2.img-ramdisk.cpio.gz: decompression OK, trailing garbage ignored
462 blocks[/B]
extracted ramdisk contents to directory mtd2.img-ramdisk/
Is this warning expected? Is safe to continue?
Also, I've found that the size of the modified packed image is far smaller than the original one
Code:
$ ll mtd2.img mtd2-modified.img
-rwx------ 1 ris ris 2621440 2009-01-07 19:19 mtd2.img
-rw-r--r-- 1 ris ris 1533952 2009-01-07 20:49 mtd2-modified.img
Update: I've tried anyway.
For the record, I've obtained the boot.img using cat, uncompressed with the perl script, modified default.prop, repacked with the perl script.
As you see from the code above, the img file is much smaller (Opening with a hex editor you can see that the end of the original image is full of 0xFF, so I believe it's ok, both the gzip warning and the different file sizes).
Reflashed it from recovery mode, using
fastboot flash boot mt2-modified.img
fastboot reboot
... and worked flawlessly
I'm leaving the coment for future references.
Thanks for the tutorial

[RiS] said:
gzip: ../mtd2.img-ramdisk.cpio.gz: decompression OK, trailing garbage ignored
462 blocks
Is this warning expected? Is safe to continue?
Click to expand...
Click to collapse
Yes, you would expect trailing zeroes, which would give you that error. The trailing zeroes exist in order to pad the image size to the nearest page boundary. They are added by mkbootimg.
[RiS] said:
Also, I've found that the size of the modified packed image is far smaller than the original one
As you see from the code above, the img file is much smaller (Opening with a hex editor you can see that the end of the original image is full of 0xFF, so I believe it's ok, both the gzip warning and the different file sizes).
Click to expand...
Click to collapse
Yep, that's exactly why. Nothing to worry about.
Thanks for the informative clarification.

alansj said:
There is also another important file you should know about. In /system/recovery.img there is a full copy of everything that is loaded on mtd1. This file is automatically flashed onto mtd1 every time you shut down. That means two things: 1. Any changes you make directly to /dev/mtd/mtd1 get blown away on reboot and 2. If you want to change /dev/mtd/mtd1 you're probably better off just sticking the image in /system/recovery.img and rebooting.
Click to expand...
Click to collapse
I'm using an stock ADP1, and the file /system/recovery.img does not exist. Is this expected?
Also, I've found out in JFv.1.31 that the recovery image is in /data/recovery.img (although there is no /data/recovery.img in my ADP1 neither..)

[RiS] said:
I'm using an stock ADP1, and the file /system/recovery.img does not exist. Is this expected?
Also, I've found out in JFv.1.31 that the recovery image is in /data/recovery.img (although there is no /data/recovery.img in my ADP1 neither..)
Click to expand...
Click to collapse
It deletes it after it flashes on the first bootup after you apply the update.

JesusFreke said:
It deletes it after it flashes on the first bootup after you apply the update.
Click to expand...
Click to collapse
Are you refering to /data/recovery.img or /system/recovery.img? or both?

[RiS] said:
Are you refering to /data/recovery.img or /system/recovery.img? or both?
Click to expand...
Click to collapse
I'm referring to /data/recovery.img in JFv1.2 and up (although there was a bug in the RC8 version of JFv1.2 that prevented it from being deleted)

So is there any reason why there is no /system/recovery.img on my ADP1?

When I use the unpack script on JF1.31 boot.img, it prints out like this:
"Could not find any embedded ramdisk images. Are you sure this is a full boot image?"
Any help?

[RiS] said:
So is there any reason why there is no /system/recovery.img on my ADP1?
Click to expand...
Click to collapse
Stock or JFv1.3?

JesusFreke said:
Stock or JFv1.3?
Click to expand...
Click to collapse
"Stock". I've just modified boot img to change default.prop

[HOW-TO] ROM-HACKING: init.rc ext2-auto-mount / ROM Signing / ROM Kitchen

AS MENTIONED IN THE INTRODUCTION TEXT THIS HAS ONLY BEEN TESTED ON AMON RA ROM 1.6.2 BUT SHOULD REALLY WORK ON ANY ROM THAT HAS NO EXT2 AUTO-MOUNT. AND YEAH THIS WHOLE PROCESS HAS BEEN DONE ON A 32a BOARD. FOR THOSE THAT TRY THIS ON OTHER ROMS LET ME KNOW HOW IT GOES.
I've searched and shuffled through the entire forum and made inquiries to ROM authors without much light being shed on this issue. I doubt I am the only one who has been looking for a way of doing this so I decided to do a small HOW-TO. Here I will explain step by step as to how you can implement a script to be part of your ROM that will auto mount an ext2 partition on boot up if such partition is present. I have included all the tools I've used in order to pull this off, and as the title suggests this has only been done on Amon Ra's latest 1.6.2 ROM. In order to follow these instructions you are expected to allready have set up an adb enviroment on your linux box and for the signing process to work you must have sun-java present, the gnu java wont work. And of course a microSD card with an ext2 partition
1. Download install.sh to your home directory
Code:
wget http://www.grindhouse.no/androidtools/install.sh
chmod a+x install.sh
2. Now execute the install.sh script which will create a directory to work in and download a tool and script package and unpack it.
Code:
./install.sh
When the install.sh script is done you need to move the mkbootimg preferebly to your tools directory of your SDK.
Code:
mv toolstomove/mkbootimg <path/to/sdk/tools/mkbootimg>
3. Unpack the RA1.6.2 ROM into a directory in your home dir. In this HOW-TO we will use directory name "ra1.6.2" as an example through out the entire process.
4. Copy the boot.img from ra1.6.2 to the ROM-cooker dir
Code:
cp $HOME/ra1.6.2/boot.img $HOME/ROM-cooker/boot.img
cd $HOME/ROM-cooker
5. Use unpack.pl to extract the ramdisk from the boot image. I've modified the script a little so it automates the entire process and decompresses the ramdisk to a directory
Code:
./unpack boot.img
6. Now you can either replace the init.rc file here with the one I've included in this package or you can add these lines by yourself. In wich case do the following
Code:
cd boot.img-ramdisk
pico init.rc
Press CTRL+w and then CTRL+t and input 27. hit enter. This will take you to line 27 of init.rc so you can add a line right before the init process remounts the rootfs in read-only mode. Add following line:
Code:
mkdir /sdext2 0771 system system
Now scroll down to the end of the init.rc file and add the following:
Code:
service mountsdext2 /system/bin/mountsd
user root
group root
oneshot
7. You have now edited (or replaced) your init.rc file and prepared it to execute a script on boot that will detect an ext2 partition and boot it if there is one to be found. Now you have to make the mountsd script a part of the ROM. Do the following:
Code:
cd $HOME/ROM-cooker
mv toolstomove/mountsd $HOME/ra1.6.2/system/bin/mountsd
rm -rf toolstomove
8. Now that the init.rc file is sorted out and mountsd has been placed in /system/bin of the ROM so it is time to re-pack the boot.img:
Code:
cd $HOME/ROM-cooker
./repack boot.img-kernel boot.img-ramdisk boot.img
rm $HOME/ra1.6.2/boot.img
mv boot.img $HOME/ra1.6.2/boot.img
9. Your ROM now has a new boot image with an updated init.rc and the /system/bin dir has the script needed to auto-mount the microsd ext2. Now you must re-zip the ROM and sign it. Do the following:
Code:
cd $HOME/ra1.6.2
zip -r update.zip *
mv update.zip $HOME/ROM-cooker/update.zip
cd $HOME/ROM-cooker
./sign.pl update.zip
10. The ROM is now signed and you now have a file called update-signed.zip. Connect the phone to your computer and execute thus:
Code:
./push update-signed.zip
11. Now you are ready to flash the modified ROM which will auto-mount an ext2 partition on your microSD. There is no need to wipe before flashing. If you have no prior experience with ROM flashing or whatever just backup your current install. If you're using OpenHOME or anything similar, nothing will be changed or damaged but if you're using MontAlbert's themes with the ROM you will have to flash them again after flashing this modified ROM.
Code:
adb reboot recovery
12. Flash from choose zip and of course choose update-signed.zip. Reboot. After the system boots up again you can now check whats what with either one of the commands:
Code:
[email protected]:~$ adb shell mount | grep sdext2
/dev/block/mmcblk0p2 on /sdext2 type ext2 (rw,noatime,nodiratime,errors=continue)
[email protected]:~/boot$ adb shell busybox df -h | grep sdext2
/dev/block/mmcblk0p2 893.7M 13.0K 846.0M 0% /sdext2
13. Voila! Your RA 1.6.2 ROM now detects and mounts your microSD ext2 partition on boot. Woohoo?
I hope the HOW-TO was easy reading and that you have succeeded in hacking up your ROM. I know that certain ROMs have this as a built-in function but Amon Ra's does not. But since alot of people including myself use his ROM because of the high speed and stability I thought I should contribute to his project and add a cool (and missed?) function to it.
Mind you that you can use the ROM-cooker set to further adjust and hack up the ROM as you see fit. Happy learning!

Very nice!
Now the question many people will ask : why would you automount ext2 if you don't use apps2sd ?

I personally have ubuntu on my ext2 And besides this approach can be used for a number of things, people who have had the need, or wanted to experiment with init.rc doing things on boot, the mountsd script can easily be altered to do what ever needed.
For me its been a learning curve finding these things out, so by sharing it I may spare some people breaking their backs over this whole init.rc thing. people may want to modify init.rc for whatever reason, so I'm sure people wont have a problem finding a way of putting this to use, and its a subject that isnt all that covered on the forum .. and hey .. at least they get a rom kitchen out of the whole shabang

Very interesting! Thank you.
I used your unpack-program to unpack a recovery-image. It seems to work fine. What I am trying to do is change the state the recovery-image returns the phone to. Would it be possible to just replace your mountsd-script with, for example, a script that installs apps? Or is there a better way to do what Im trying to achieve?
Cheers,
edit: I noticed that on the emulator it is sufficient to just place an apk-file in "data/app" to get it installed. Could it be possible that this is all I need a script to do? :O or could I hurt my poor phone by doing so you think?

sandis84 said:
edit: I noticed that on the emulator it is sufficient to just place an apk-file in "data/app" to get it installed. Could it be possible that this is all I need a script to do? :O or could I hurt my poor phone by doing so you think?
Click to expand...
Click to collapse
That's indeed all you need to do.

Hi!
So I tried to create a signed update.zip, but it failed. It didnt create a "update-script"-file, so my device refused to install it. I wrote my own "update-script"-file, but then it complained "no digest" for the file. How do I solve this?

post the contents of your script people might see whats up

so is this all on linux?
also where are the script files for your tutorial
thanks for the time to put together

sitimber said:
so is this all on linux?
also where are the script files for your tutorial
thanks for the time to put together
Click to expand...
Click to collapse
Says where its at in the first line : )
Code:
wget http://www.grindhouse.no/androidtools/install.sh
But now that I checked, I have to apologize, I see I have a missed payment with my hosting, I'll fix that within the day. Also sorry I havent been answering the few questions here I've been afk cause of surgery.

sitimber said:
post the contents of your script people might see whats up
Click to expand...
Click to collapse
well, I looked in another "update-script" file and found this:
assert compatible_with("0.2") == "true"
assert getprop("ro.product.device") == "dream" || getprop("ro.build.product") == "dream"
show_progress 0.5 0
write_radio_image PACKAGE:radio.img
show_progress 0.5 10
Click to expand...
Click to collapse
So I figured that nothing was essential other then the line "write_radio_image PACKAGE:radio.img". Also ofcourse I made sure it contained the name of my image-file instead of "radio.img". This gave me the "no digest" message, so now I feel unsure on how to create a working update.zip.
edit:
SOLVED! How silly of me. When you sign the update, a hash of each file is put in manifest.mf. Since I added the update-script after signing the file, ofcourse the digest(hash) was missing. Now everything works alot better and I can proceed... until I get stuck again
Cheers,
edit2:
Just to get a better understanding, what exactly does each line do here? Or where can I read about this?
Code:
service mountsdext2 /system/bin/mountsd
user root
group root
oneshot
edit3:
Ok, so I have experimentet, but I still dont manage to solve those last steps. I tried to edit init.rc and just add "mkdir /testdir 0000 system system" where the other directories were created. I then repacked it, zipped it, signed it, put it on my sdcard, started up a custom recovery, installed the update and rebooted. Everything seems to work fine. But when I start adb and check around, I dont see the "testdir"-directory. Also when I check in init.rc my line is gone. Do you guys have an idea of where I went wrong?

sitimber said:
so is this all on linux?
also where are the script files for your tutorial
thanks for the time to put together
Click to expand...
Click to collapse
it doesnot necesarily have to be linux ...you can also do it in windows using cygwin and dsxda's android rom kitchen

[Guide] How to create EXT4 images.

Since most of the high-end devices are using now EXT4 partitions i decided to make a guide.
I am doing this because this is the easiest way to create an EXT4 image.
This is not my guide I am just adapting and make it clear to everybody; someone showed me how to do this (I will mention him at the end of the guide).
Let's assume that you dumped the system.img from your own device and you want to add something to it.
We will create a new system.img and we will name it system_new.img, the size will be 240 Mb.
Step 1
Linux Machine (I used Ubuntu)
We prepare the directories and copy the system.img in the folder in which we will work.
mkdir system (here we will mount the old system.img
mkdir system_new (here we will mount the system_new.img)
Step 2 – Creation of the actual EXT4.img
dd if=/dev/zero of=system_new.img bs=4k count=60000
Translation of the terms,
bs =blocksize, 4k= the size of the block`s which in this case is 4kb
count=60000, the number of block`s, in our case will result an image of 240 Mb.
The blocksize can be 1k/2k/4k/16k
To get the exact size of the image that you create use simple maths.
60000 * 4 = 240000
Step 3 Formating the system_new.img with EXT4
mkfs.ext4 system_new.img
It will be a question where you will select yes (Y)
We override the file system check (If you don`t do this, the image will not work)
tune2fs -c0 -i0 system_new.img
Step 4 We mount the directories that we previous created.
mount -o loop system_new.img system_new/
mount -o loop system_new.img system/
Step 5 We copy the content from the old system.img in the system_new.img
cp -v -r -p system/* system_new/
We sync the files
sync
Step 6 Unmounting the partitons.
umount system_new/
umount system/
Step 7 Enjoy your new ext4 system.img
Tips:
If you are using Ubuntu just type
sudo su
And you will be root and no more sudo at each command.
You can add new files in the new created system.img but you need to set the permissions and ownership properly, otherwise it will not work.
Credits: arctablet.com administrator.

work perfect!
I managed to create a new system img for huawei phone.

Errors in Step 3 and 4: Unable to proceed
Hi There,
I am getting errors in step 3 and 4.
Step 3 Formating the system_new.img with EXT4
mkfs.ext4 system_new.img
It will be a question where you will select yes (Y) -- after this below error comes
Device size reported to be zero. Invalid partition specified, or partition table wasn't reread after running fdisk, due to a modified partition being busy and in use. You may need to reboot to re-read your partition table.
We override the file system check (If you don`t do this, the image will not work)
tune2fs -c0 -i0 system_new.img -- after this below error comes
Attempt to read block from filesystm resulted in short read while trying to open system.img
Step 4 We mount the directories that we previous created.
mount -o loop system_new.img system_new/ -- after this below error comes
unknown filesystem type 'ext4'
Could you please help.

i whant to create and system.img.ext4 for my android ! ! But i saw that image which is created is just system.img ! I`m using ubuntu and i whant to know what is need it to create that system.img.ext4 ! I don`t see that img to be ext4 file ! Thanks

jabarel said:
i whant to create and system.img.ext4 for my android ! ! But i saw that image which is created is just system.img ! I`m using ubuntu and i whant to know what is need it to create that system.img.ext4 ! I don`t see that img to be ext4 file ! Thanks
Click to expand...
Click to collapse
I'm not sure but it's probably just a matter of file extenstion.
By the way, great tuto. May be someting to add :
Android ext4 don't seem to be the exact standart of linux ext4 file systems.
To make it fully compatible and usable with fastboot, the use of "ext2simg" can be useful.
So it will be something like this :
ext2simg fs2convert.img fsconverted.img
ext2simg can be found in android-tools in debian repository.

I am porting a rom ,i extracted "system.new.dat" into "sytem" folder , applied changes according to this guide to port a ROM -->> http://forum.xda-developers.com/showthread.php?p=65933478#post65933478
can you tell me how to reconstruct the "system.new.dat" from "sytem" folder ?

is mkfs.ext4 applet available to arm devices..??

you can do it faster...
Great if you create a new image, but to edit no need to create all these steps ...
Just copy the system.img to system_new.img and mount that one and edit..

There's no clear instruction!
Hours of researching many places and no good instruction about how to create or edit an EXT4 with or without Linux!
I know this is an old post but I just wanted to try, might get a reply!

Frank2406 said:
Hours of researching many places and no good instruction about how to create or edit an EXT4 with or without Linux!
I know this is an old post but I just wanted to try, might get a reply!
Click to expand...
Click to collapse
what is not clear?
this has been tested by me and it works.
there are more refined ways in doing it, it just depends on what you need to to with the ext4 image.

globula_neagra said:
what is not clear?
this has been tested by me and it works.
there are more refined ways in doing it, it just depends on what you need to to with the ext4 image.
Click to expand...
Click to collapse
Step 1: "We prepare the directories" you said. What directories?
"mkdir system"
"mkdir system_new" which, what or where are they?
Step 2: The whole step 2 for a newbie in Linux like me is bla bla bla except the title "Creation of the actual EXT4.img"!
And the rest of your guide is as the same as step 2 which I mentioned.
And if this guide is for Ubuntu experts then maybe in the beginning you could mention so people don't get their hopes up dear globula_neagra!!
Long story short, I just wanted to try a custom Rom on my Zenwatch 1, but I've forgot to make backup, so the official Rom was gone. Asus itself didn't help to get a copy of the official one, so I tried Anthias custom Rom instead, but that made the watch even worse.
Then I started to research how to fix it, so I found this article.

It s not a step by step guide on how to use ubuntu.
I assume that wheen you want to learn something you do use google too. For this instance i would google in this way "what does mkdir command in ubuntu"
After i understood the purpose of the command and how to use it i would try to apply it using the guide and after that you will see that things will start to make sense.
My guide was written with the idea that if you use android you have an idea of linux too and in this case ubuntu.
The command line in linux is somewhat similar to the one in windows commander there are some extra things that you need to learn but those can t be put in a guide like this.
In regards to your watch. My advice is to find another one and take a system dump from that one and flash it to yours if you have an unlocked bootloader.

Here you cand find some good reads on how to dump the files from the watch. And a bit more details on what is the business with the ext4 creation. Topic is5 years old but still relevant.
http://www.arctablet.com/blog/forum/arnova-7c-g3/arnova-7c-g3-dev-topic/

Extract files from stock firmware images

Hi,
when I still hadn't the device, I wanted to know exactly what's included in stock ROMs to have a better idea of what to expect. I hence downloaded a stock firmare and the stock system.img (see below for the steps).
Ok, so what? Well, when KK was released I decided to do the same (I was still waiting for the device), but I couldn't. Unlike before, I didn't find a single system.img, but multiple files (3 to be exact, maybe it's too big to be flashed at once with fastboot, I don't know, I'm new to this) and couldn't understand how the original image was splitted to generate those files.
Did anyone see something similar already and sucesfully merged splitted filesystems?
I know I could simply ask for a system dump (or wait for KK), but now I'm curious to know on how to do this. I tried few things but I couldn't find any way to do it. Maybe I could see how fastboot treat these files, but I wonder if anyone already knows the answer.
Anyway, here the steps to mount the system.img of our stock JB firmwares. Maybe there's an easier way, I honestly don't know. As far as I know, converting the sparge image should be enough, but I had to do more:
Code:
#Convert sparse image with simg2img
simg2img system.img system.img.raw.tmp
#UTF8 may slow down grep, switch to C
export LANG=C
#Look for the ext4 magic and calculate its position
magic=`grep -aobP -m1 '\x53\xEF' system.img.raw.tmp | head -1 | cut -d":" -f1`
offset=$(($magic-1080))
#Remove extra header with dd
dd if=system.img.raw.tmp of=system.img.raw ibs=$offset skip=1
#Remove temp file
rm system.img.raw.tmp
Now you can mount system.img.raw as a normal ext4 filesystem.

Just concatenate the three chunks together like so:
Code:
cat system.img_sparsechunk1 system.img_sparsechunk2 system.img_sparsechunk3 > system.img
Then apply the steps from the OP and voilà!
Edit: Scratch that: the image is accessible, some files are visible but others are missing. To be continued...

Darkshado said:
Just concatenate the three chunks together like so:
Code:
cat system.img_sparsechunk1 system.img_sparsechunk2 system.img_sparsechunk3 > system.img
Then apply the steps from the OP and voilà!
Edit: Scratch that: the image is accessible, some files are visible but others are missing. To be continued...
Click to expand...
Click to collapse
As you have found that doesn't work, remember that each file will have metadata headers so that may be one reason you can't just cat them together.
To OP - can't you just mount each img as a filesystem and copy all the files from each mounted filesystem to another entirely separate directory. At least that way you have all the files in one place, eg copy
/sparsechunk1/system/file1 to /newdir/system/file1
And so on.

scott_doyland said:
As you have found that doesn't work, remember that each file will have metadata headers so that may be one reason you can't just cat them together.
To OP - can't you just mount each img as a filesystem and copy all the files from each mounted filesystem to another entirely separate directory. At least that way you have all the files in one place, eg copy
/sparsechunk1/system/file1 to /newdir/system/file1
And so on.
Click to expand...
Click to collapse
Only the first chunk can be mounted, the other two are not recognized as filesystem and there's no way to mount them.
It's not as if /system was divided in three parts and then an image for each one was created, so that you can treat them as separate files (what you said would work in this case).
One image is created and then it's splitted in three in some unknown way. The first image is the one that holds the informations to access the files, the other two just pieces of files that can't be accessed without the informations in the first chunk.
mfastboot knows how to correctly copy the data from the separate images with the right offsets inside the phone so that in the end all the files can be accessed. Concatenating the files using dd using the correct offsets could maybe work, but after a few attempts I gave up.

There is method to extract files under Windows

Al936 said:
There is method to extract files under Windows
Click to expand...
Click to collapse
Any change you happen to be willing to share the contents of or principles behind `sparse2img.exe`?

HolySid said:
Any change you happen to be willing to share the contents of or principles behind `sparse2img.exe`?
Click to expand...
Click to collapse
What kind of principles you expect from me? I just posted the link to one of the method to extract all files and folders from stock firmware's system partition. The tools were not developed by me - I just informed XDA community about it. As you can see from the tread several persons already confirmed that it works.

Al936 said:
What kind of principles you expect from me? I just posted the link to one of the method to extract all files and folders from stock firmware's system partition. The tools were not developed by me - I just informed XDA community about it. As you can see from the tread several persons already confirmed that it works.
Click to expand...
Click to collapse
Oh, I'm sorry, I thought it was your work. I just want to know how to merge the system files. I know the exe is working, but I'm running Linux, so my question it is both out of curiosity and simply because I cannot run the code.

Try running it with wine or in virtual machine.
sent via tapatalk

Thanks, I managed it by using another laptop. But still, I'd rather know what happened
Sent from my XT1032 using xda app-developers app

Darkshado said:
Just concatenate the three chunks together like so:
Code:
cat system.img_sparsechunk1 system.img_sparsechunk2 system.img_sparsechunk3 > system.img
Then apply the steps from the OP and voilà!
Edit: Scratch that: the image is accessible, some files are visible but others are missing. To be continued...
Click to expand...
Click to collapse
I just replaced the first line in the OP's instructions with this to join the system.img_sparsechunk files:
Code:
simg2img system.img_sparsechunk.* system.img.raw.tmp
And then the rest worked fine. Here were the exact steps I took (I shortened it a tiny bit, but it's the same concept):
Code:
simg2img system.img_sparsechunk.* system.img.raw.tmp
offset=`LANG=C grep -aobP -m1 '\x53\xEF' system.img.raw.tmp | head -1 | awk '{print $1 - 1080}'`
dd if=system.img.raw.tmp of=system.img.raw ibs=$offset skip=1
sudo mkdir /mnt/system
sudo mount system.img.raw /mnt/system

SenorChang said:
I just replaced the first line in the OP's instructions with this to join the system.img_sparsechunk files:
Code:
simg2img system.img_sparsechunk.* system.img.raw.tmp
And then the rest worked fine. Here were the exact steps I took (I shortened it a tiny bit, but it's the same concept):
Code:
simg2img system.img_sparsechunk.* system.img.raw.tmp
offset=`LANG=C grep -aobP -m1 '\x53\xEF' system.img.raw.tmp | head -1 | awk '{print $1 - 1080}'`
dd if=system.img.raw.tmp of=system.img.raw ibs=$offset skip=1
sudo mkdir /mnt/system
sudo mount system.img.raw /mnt/system
Click to expand...
Click to collapse
It worked. Thank you!

[Q] Need help with "repack-zimage.sh" - repacked file too large

Hi all,
My Samsung Stratosphere (yeah I know it is old) recently had a hw issue with the Movinand. I cannot access any devices off mmc0. I figured out i can bypass the movinand and remount the mmcblk0 partitions to my external SD card. I also figured out I need to reconfigure my init.rc file (and some others) to do this. I have used the "repack-zimage.sh" tool to extract my initramfs from my zimage kernel. The problem I am having is that the script unpacks things fine..but when I try to repack the initramfs back into zimage, the script stops and gives me the following error:
The command used was "$/ sudo bash repack-zimage.sh -p"
Error: repack-zimage.sh: piggy.gz too large (gzip -9: +689, gzip -8: +1330)
You might want to try a different combination of the -g, -r and -s options.
I ran the repack-zimage using the bash command..and am using Ubuntu 14.04 (if that helps)
The funny thing is I made no changes to any of the initramfs files..I was just testing the script to see if it would unpack and repack correctly.
The reference thread is: [script] repack-zImage.sh: Unpack and repack a zImage without kernel source, V. 5
I know the thread is old, but since I am a new member, I cannot reply within the thread..I was recommended to post here...Sorry if it is in the wrong place.
Any ideas on why the repacked file is larger and how can I modify the script or anything else to correct this issue. When this gets working, I can move onto the next part of the "fix"..and hopefully get my phone working..
Thanks!
EDIT: I was able to get the file repacked..but had to choose "-r" as an option..which means things are not repacked in the same order as the original zImage...So the question is...does it matter? Will the system know the components are "out of order" and deal with it?..or will this cause a problem in the booting sequence?