[General Questions and Answers] 'Artemis':
(Android 7.0, Shield Tablet)

I found myself in the situation of having to back up my data without root multiple times, and till now everything went pretty well.

Regarding apps and relative data (on data/data), I use Helium(1) which performs a per-app adb backup with apk, similar to what Adebar(2) does, then I restore them individually using the "adb restore" command (restore through Helium never worked for me).

This worked flawlessly till now.

I regularly backed up my apps, and respective ".adb" files of believable size were created, then, after a data wipe, i proceeded to restore my backups, but I found out they weren't restoring right. Here's the "adb restore" log, received trough logcat:

adb logcat -s BackupManagerService

07-17 19:14:39.562 759 2184 I BackupManagerService: Beginning full restore...
07-17 19:14:39.604 759 2184 D BackupManagerService: Starting restore confirmation UI, token=761002928
07-17 19:14:39.620 759 2184 D BackupManagerService: Waiting for full restore completion...
07-17 19:14:41.125 759 3508 D BackupManagerService: acknowledgeFullBackupOrRestore : token=761002928 allow=true
07-17 19:14:41.127 759 16894 I BackupManagerService: --- Performing full-dataset restore ---
07-17 19:14:41.142 759 16894 I BackupManagerService: Package org.fdroid.fdroid not installed; requiring apk in dataset
07-17 19:14:41.144 759 16894 D BackupManagerService: APK file; installing
07-17 19:14:41.144 759 16894 D BackupManagerService: Installing from backup: org.fdroid.fdroid
07-17 19:14:41.968 759 16894 D BackupManagerService: [discarding file content]
07-17 19:14:41.968 759 16894 D BackupManagerService: [discarding file content]
07-17 19:14:41.969 759 16894 D BackupManagerService: [discarding file content]
07-17 19:14:41.969 759 16894 D BackupManagerService: [discarding file content]
07-17 19:14:41.969 759 16894 D BackupManagerService: [discarding file content]
07-17 19:14:41.969 759 16894 D BackupManagerService: [discarding file content]
07-17 19:14:41.969 759 16894 D BackupManagerService: [discarding file content]
07-17 19:14:41.969 759 16894 D BackupManagerService: [discarding file content]
07-17 19:14:41.970 759 16894 D BackupManagerService: [discarding file content]
07-17 19:14:41.970 759 16894 D BackupManagerService: [discarding file content]
07-17 19:14:41.971 759 16894 D BackupManagerService: [discarding file content]
07-17 19:14:41.971 759 16894 D BackupManagerService: [discarding file content]
07-17 19:14:41.971 759 16894 D BackupManagerService: [discarding file content]
07-17 19:14:41.972 759 16894 D BackupManagerService: [discarding file content]
07-17 19:14:41.972 759 16894 D BackupManagerService: [discarding file content]
07-17 19:14:41.973 759 16894 D BackupManagerService: [discarding file content]
07-17 19:14:41.976 759 16894 D BackupManagerService: [discarding file content]
07-17 19:14:42.548 759 16894 D BackupManagerService: [discarding file content]
07-17 19:14:42.548 759 16894 D BackupManagerService: [discarding file content]
07-17 19:14:42.548 759 16894 D BackupManagerService: [discarding file content]
07-17 19:14:42.549 759 16894 D BackupManagerService: [discarding file content]
07-17 19:14:42.549 759 16894 W BackupManagerService: Saw type=0 in tar header block, info=FileMetadata{null,0,null:,0}
07-17 19:14:42.550 759 2184 I BackupManagerService: Full restore processing complete.
07-17 19:14:42.551 759 16894 D BackupManagerService: Full restore pass complete.

Here I tried to restore the FDroid app, for example, and I see a lot of weird "[discarding file content]" messages. So, I tried to restore them with Titanium Backup, but it showed me this empty screen:

I tried to export an ".adb" file to a ".tar" file too, using this tool(3), but all I got was a META-INF folder with a MANIFEST.MF file.

Are my adb backups irreversibly corrupted?

Edit: I perfectly know that I shouldn't rely on non-root backup systems, but I unexpectedly lost root privileges after the infamous SuperSu v2.80 update, and I ended up with a corrupted boot image, so this was all I could do. I completed successfully the same process other times before, before deciding to root my device.

Urls:

https://play.google.com/store/apps/details?id=com.koushikdutta.backup - Helium app playstore page

https://github.com/IzzySoft/Adebar - Adebar's github page

https://sourceforge.net/projects/adbextractor/ - .adb to .tar extractor