I want to restore a TWRP backup on my Samsung Galaxy S6 (SM-G920F), to get back from a custom ROM (9.0) to Stock (7.0).

Restoring /system goes fine, but TWRP throws an error when it comes to restore /data : "extractTarFork() process ended with ERROR: 255 My question is : can I restore only /system and boot my original ROM ? If that doesn't work, how can I fix this error ? (I don't have a sdcard)

  • Don't you get an option to select which partitions to restore? And that error seems to be related to tar utility. You can try unpacking backup file manually using updated tar. Oct 24, 2018 at 22:55
  • 1
    While restore, it shows checkboxes under each partition name. Like /boot, /system, /data. You can uncheck /data. But, I recommend, restore all partitions. It will restore to your device to stock ROM, and then you can perform a reset to delete user data.
    – Rahul Gopi
    Oct 25, 2018 at 0:03
  • @Irfan Latif : sure, I can choose what to restore, my question was : if I only restore /system (after wiping system, data, and cache of course), will my phone be able to boot on the stock ROM ? For the error, I googled a bit and it could be related to missing space on the phone, or just because /data is mounted (and I cannot unmount it because my backup is in internal storage), that's why I was asking if restoring only system would let me boot
    – EinderJam
    Oct 25, 2018 at 5:18
  • Definitely, device will boot with clean /data partition. Complete Android OS lives in /system and /boot. But without /data, you will lose your personal apps, apps data, settings etc. Oct 25, 2018 at 7:49
  • If you are unable to restore /data due to space limitation and you don't have sdcard as well, then restore /system and /boot first and then delete those files from backup (make sure those are correctly restored). It will spare space on internal memory and then you can restore /data. If still there is shortage of space, you can put your backup file on a PC and extract the backup to /data partition after mounting /data through USB Mass Storage. It needs a PC with Linux or a phone with USB OTG support may also work. Ask if further help required. Oct 25, 2018 at 7:57

1 Answer 1


[Can] I restore only /system and boot my original ROM ?

It depends upon what lies in the backup. If you took the backup of your stock ROM and you're referring to the same backup, then yes, restoring /system using that particular backup would restore stock ROM. But you would need to restore /boot as well since that is part of stock ROM too.

However, if you must restore a different ROM, even if it is a stock ROM, it is a good practice to do a clean flash or atleast overwrite existing /data and /cache files with the ones in the backup to avoid conflict between various versions of files/apps which can cause bootloop or battery drain or whatnot.

In your case, since you cannot restore /data from the backup, I advise you to take a complete backup of your current ROM (including userdata), then reset /data (except /data/media) and /cache, and then restore /system and /boot from stock ROM backup. In this way, you would end up with a pristine stock ROM and can always restore /data when you manage to fix that error you mentioned. This is the path of least problems.

  • Thank you so much ! I just have one more question : When I made my backup, TWRP didn't offered me the option to backup /boot (only /system,/data,cache,modem,etc...). Is /boot included in /system backup ? If not, I'll be facing a big problem...
    – EinderJam
    Oct 25, 2018 at 12:04
  • It is strange that TWRP didn't offer boot to be backed up. No, it has to be backed up specifically and is not included in /system. You can get the boot image if you search the stock ROM for your device on the internet. Normally, custom kernels including that of custom ROMs for a device works with stock ROM too. In an extreme case, all that would happen is that you might end up getting stuck in a boot loop or on Android boot logo or on OEM logo, or your OS might start crashing apps or the OS for no good reason.
    – Firelord
    Oct 25, 2018 at 14:47
  • To avoid that, I think I'll just flash the stock ROM with Odin. I'll lose my apps and settings, but I have some SmartSwitch backups that I'll be able to restore afterwards. Could you tell me where to look for my stock ROM file and how to flash it with Odin ? I'm a bit lost where it comes to choose between BL,AP and so on
    – EinderJam
    Oct 25, 2018 at 16:12
  • Sorry, I have no idea where to look for stock files for Samsung devices as I do not own one. I believe XDA forums can help in that regard. Good luck. :-)
    – Firelord
    Oct 25, 2018 at 18:31

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