I noticed that for some system apps (for example chrome, which is preinstalled by default on my device) I can't do adb backup . Doing so results in the 47 bytes dummy .ab file. I checked in manifest they have allowBackup="true".

Eg for chrome this is:

allowBackup="true" backupAgent="org.chromium.chrome.browser.ChromeBackupAgent" extractNativeLibs="false" fullBackupOnly="false".

Why this is happening? How can I backup such apps' data without root? PS: Helium backup doesn't show system apps.


I found the reason in logcat while performing an backup:

BackupManagerService: Package com.android.chrome is key-value.

By default for abd backup keyvalue backups are disabled:

"/system/bin/bu" (the command that is called on-device by adb backup) help text: 

 -keyvalue|-nokeyvalue: include apps that perform key/value backups.
     (default -nokeyvalue)

Therefore you need to include the -keyvalue option to create a chrome backup:

adb backup -keyvalue -f chrome.ab com.android.chrome

This creates a backup file that contains only the chrome settings (no cache files, cookies, local data ...)

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