How to Unpack and Recompile system.img.ext4.lz4? - Samsung Galaxy S9+ Questions & Answers

As the title suggests, is it possible to unpack and recompile the System.img.ext4.lz4 found within the stock system image? I'd like to poke around with stuff and see what happens. I know it probably won't accomplish anything but let a boy dream I can't fine any guides out there that work for this but hopefully a dev will bless me with his magic.

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If you go to android software and hacking forum here on xda you might see what you're looking for. It's a devs section.

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Nathamio said:
As the title suggests, is it possible to unpack and recompile the System.img.ext4.lz4 found within the stock system image? I'd like to poke around with stuff and see what happens. I know it probably won't accomplish anything but let a boy dream I can't fine any guides out there that work for this but hopefully a dev will bless me with his magic.
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Use 7zip lz4 to extract img then mount img in Linux and then you can access raw system. I can extract and upload it for you if you want to give me the file name for the firmware.

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VICosPhi said:
Use 7zip lz4 to extract img then mount img in Linux and then you can access raw system. I can extract and upload it for you if you want to give me the file name for the firmware.
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If I mount it in linux can I modify it without having to write it to a new img? I tried mounting it and it won't work. Is there some special tool I need to install?

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You extracted the xxx.ext4.lz4 to xxx.ext4 then again extracted xxx.ext4 to xxx.img using 7zip LZ4 before mounting to Linux, correct?

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VICosPhi said:
You extracted the xxx.ext4.lz4 to xxx.ext4 then again extracted xxx.ext4 to xxx.img using 7zip LZ4 before mounting to Linux, correct?
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I am also having an issue repacking the image as odin says invalid lz4.
I'm trying to but I get this error:
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I haven't tried modifying and repacking the file yet, but what I did was extracted the lz4 to ext4 and then ext4 to img using 7zip LZ4. Then I mounted the img in CentOS and copied the /system folder over to get it Deodexed. Someone posted the other day that you can repack an IMG file and just flash it as IMG without having to convert to EXT4 or LZ4 on an S8 with v2 bootloader. I don't think this has been tested on a newer or v3 bootloader like S9.

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Micro-instruction for unpack lz4 formats
-Download lz4 programm in attach. Extract in any folder.
-Put in lz4 folder system.img.ext4.lz4
-Open CMD line for lz4 folder and write:
lz4.exe -d system.img.ext4.lz4 system.img.ext4
-wait
-Done. We have system.img.ext4.
Now we can unpack this with SVAImgUnpack or any tool

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mahotlov said:
Micro-instruction for unpack lz4 formats
-Download lz4 programm in attach. Extract in any folder.
-Put in lz4 folder system.img.ext4.lz4
-Open CMD line for lz4 folder and write:
lz4.exe -d system.img.ext4.lz4 system.img.ext4
-wait
-Done. We have system.img.ext4.
Now we can unpack this with SVAImgUnpack or any tool
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Click to collapse
nope decoded but linux reader not work, svaimg not work is oreo

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bleros said:
nope decoded but linux reader not work, svaimg not work is oreo
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I just converted the S7 Oreo Image (BTU-G930FXXU2ERD5) on my debian linux machine. To convert the android sparse file to the raw ext4 image, both worked simg2img and SVAImgUnpack.exe.
Which step does not work? The lz4 decompression? Or the conversion of the android sparse file to an raw ext4 image? Or the reading of the raw ext4 image?
By the way, I'm wondering if the S9 image is using ext4 or f2fs. Maybe that is the problem.

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wernerwa said:
I just converted the S7 Oreo Image (BTU-G930FXXU2ERD5) on my debian linux machine. To convert the android sparse file to the raw ext4 image, both worked simg2img and SVAImgUnpack.exe.
Which step does not work? The lz4 decompression? Or the conversion of the android sparse file to an raw ext4 image? Or the reading of the raw ext4 image?
By the way, I'm wondering if the S9 image is using ext4 or f2fs. Maybe that is the problem.
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i treid on windows , s7 oreo , no worry i have tried on vmware machine with debian and superr kitchen work fine

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End of day you will find out that once you modify the stock image, it's no longer "stock" and probably fail when you try to flash it. Integrity verification wont let you. Unless you OEM unlock and flash a custom recovery, which WILL certainly trip your knox. There is no way back. For now. (I hope.)

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wernerwa said:
I just converted the S7 Oreo Image (BTU-G930FXXU2ERD5) on my debian linux machine. To convert the android sparse file to the raw ext4 image, both worked simg2img and SVAImgUnpack.exe.
Which step does not work? The lz4 decompression? Or the conversion of the android sparse file to an raw ext4 image? Or the reading of the raw ext4 image?
By the way, I'm wondering if the S9 image is using ext4 or f2fs. Maybe that is the problem.
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i tried again work fine was my mistake first lz4 used then droped into svaimgunpack then ext4explorer :highfive:

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mahotlov said:
Micro-instruction for unpack lz4 formats
-Download lz4 programm in attach. Extract in any folder.
-Put in lz4 folder system.img.ext4.lz4
-Open CMD line for lz4 folder and write:
lz4.exe -d system.img.ext4.lz4 system.img.ext4
-wait
-Done. We have system.img.ext4.
Now we can unpack this with SVAImgUnpack or any tool
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Click to collapse
Hi,
I used 7zip to decompress firmware downloaded from sammobile (s7 edge). But the boot and recovery img I got were boot.img.lz4 and recovery.img.lz4.
I used your tool to get the .img directly without going into .ext4. Did I miss something in the steps I took? Thanks

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dknight178
Hi. This instruction I wrote for s8/s9 (+)
Their images in firmware have ext4 extension.
You're doing everything right.

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dknight178 said:
Hi,
I used 7zip to decompress firmware downloaded from sammobile (s7 edge). But the boot and recovery img I got were boot.img.lz4 and recovery.img.lz4.
I used your tool to get the .img directly without going into .ext4. Did I miss something in the steps I took? Thanks
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Click to collapse
Only certain partitions , like system and userdata, will have images that include the ext4 extension. Possibly cache, as well. Basically just the main partitions that are always mounted and regularly interacted with when the system is booted up and running.
Nathamio said:
I am also having an issue repacking the image as odin says invalid lz4.
I'm trying to but I get this error:
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The tar archives used by odin aren't the basic version that 7zip is capable of making,. You need to use an actual tar excutable, and include certain argument. On windows, your tar command should look something like this:
Code:
tar.exe --create --format=gnu -b20 --quoting-style=escape --owner=0 --group=0 --totals --mode=644 -f yourFW.tar boot.img.lz4 recovery.img.lz4 system.img.ext4.lz4 userdata.img.ext4.lz4
That would make a basic AP odin-ready tar package. Then just use md5sum to finish it off, though I don't believe its necessary Something like this:
Code:
md5sum.exe -t yourFW.tar >> yourFW.tar
move yourFW.tar yourFW.tar.md5
I attached d a zip with windows version of tar, md5sum, mv, and ls.

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I f I want to make a flashable zip, what steps would I take to extract stock firmware to do so?

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up

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mahotlov said:
Micro-instruction for unpack lz4 formats
-Download lz4 programm in attach. Extract in any folder.
-Put in lz4 folder system.img.ext4.lz4
-Open CMD line for lz4 folder and write:
lz4.exe -d system.img.ext4.lz4 system.img.ext4
-wait
-Done. We have system.img.ext4.
Now we can unpack this with SVAImgUnpack or any tool
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i had error
lz4.exe : The term 'lz4.exe' is not recognized as the name of a cmdlet, function, script file, or operable program.
Check the spelling of the name, or if a path was included, verify that the path is correct and try again.
At line:1 char:1
+ lz4.exe
+ ~~~~~~~
+ CategoryInfo : ObjectNotFound: (lz4.exe:String) [], CommandNotFoundException
+ FullyQualifiedErrorId : CommandNotFoundException

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hochocnua said:
i had error
lz4.exe : The term 'lz4.exe' is not recognized as the name of a cmdlet, function, script file, or operable program.
Check the spelling of the name, or if a path was included, verify that the path is correct and try again.
At line:1 char:1
+ lz4.exe
+ ~~~~~~~
+ CategoryInfo : ObjectNotFound: (lz4.exe:String) [], CommandNotFoundException
+ FullyQualifiedErrorId : CommandNotFoundException
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Click to collapse
wrong path and dont use powershell use cmd as admin