Backup testing
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 I have tried a few different backup solutions i found on the forums here that do not work. I am in a good position to test this as i have two pixel 3a's one for testing (cracked screen) and one for my daily driver. The few scripts I found to work are just home folder copiers which is not really a backup solution. The adb pull /data/system-data /data/system-userdata does not work from recovery. I also tried TWRP which takes the backup but wont restore on the other device. Anyone have a working solution or something I can test since i have two phones. 
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 I use to struggle with same problem but then I find this somewhere in the forum (sorry I don't remember who is the original advisor) This solution works on OPO and Volla. I also tried to migrate my settings from OPO to Volla with this but that did not work - OPO -> OPO or Volla -> Volla works fine  Source device After connecting source device on PC commands in terminal as follows: 
 Reboot phone into recovery: adb reboot recovery
 Acquire root: adb root
 Activate shell: adb shell (command prompt will change to # sign)
 Backup system-data (this will also create log files, that can be examined for possible errors) :
 tar -czpv -f /system-data.tgz /data/system-data/ >/system-data.out 2>/system-data.err
 tar -czpv -f /user-data.tgz /data/user-data/ --exclude='data/user-data/phablet/.cache' >/user-data.out 2>/user-data.err
 logout from shell to your terminal
 Ctrl+Dgo to directory where backup data are to be stored in PC 
 adb pull /system-data.tgz
 adb pull /user-data.tgzDestination device Reboot phone into recovery: adb reboot recovery 
 go to directory where backup data are to be stored in PC
 adb push ./system-data.tgz /
 adb push ./user-data.tgz /Activate shell: 
 adb shell
 tar -xzv -f /system-data.tgz
 tar -xzv -f /user-data.tgz
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 that is similar to this post 
 https://forums.ubports.com/topic/1498/backup-complete-device/9@Bastos in post number 9 says adb pull /data/system-data but my phone has nothing in that folder nothing to backup data is an empty folder? 
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 @kmsgli I am not expert on this but I have tried multiply backup methods. 
 Only one what I managed to get working 10/10 is the one what I wrote on my message.
 As far as I can tell with my experience: if you use that method you can actually restore everything (including sms, phone calls etc.) as long as you try to restore it to "same device" = not excatly the same one but OPO -> Volla did not work but OPO -> OPO working.Bastos methot is mostly the same but I have tried it also and it did not work. 
 As said I am not an expert but if you follow my message step by step you might get it working (that is what I did - I just copy&pasted someones idea ) )
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 @alaraajavamma Afaik someone is working on making a backup solution working from the installer