[Android Q&A, Help & Troubleshooting] GCalzo:
I do not know the answer to your problem, but me too I have a problem with Viber backup, basically it never ends!

For the backup I add -apk -obb and the file is about 29mb

For the logcat I add -v time and these are the backup-related entries (after I have purged the hundreds or other infos!)

03-23 18:18:02.654 I/ActivityManager( 869): Killing 5947:com.viber.voip/u0a159 (adj 15): empty #8
03-23 18:29:07.098 D/BackupManagerService( 869): Binding to full backup agent : com.viber.voip
03-23 18:29:07.165 I/ActivityManager( 869): Start proc com.viber.voip for backup android/FullBackupAgent: pid=10713 uid=10159 gids={50159, 9997, 3003, 1028, 1015, 3002, 3001} abi=armeabi-v7a
03-23 18:29:07.165 D/BackupManagerService( 869): awaiting agent for ApplicationInfo{13f43d13 com.viber.voip}
03-23 18:29:07.198 I/BackupManagerService( 869): OBB service connection com.android.internal.backup.IObbBackupService$Stub$Proxy@2c5b976f connected on com.android.server.backup.BackupManagerService$FullBackupObbConnection@2eea74e4
03-23 18:29:07.331 D/BackupManagerService( 869): agentConnected pkg=com.viber.voip agent=android.os.BinderProxy@10c3f905
03-23 18:29:07.331 I/BackupManagerService( 869): got agent android.app.IBackupAgent$Stub$Proxy@382ebd5a
03-23 18:29:07.331 I/BackupRestoreController( 869): Getting widget state for user: 0
03-23 18:29:07.346 I/file_backup_helper( 869): Name: apps/com.viber.voip/_manifest
03-23 18:29:07.346 I/file_backup_helper( 869): Name: apps/com.viber.voip/a/base.apk
03-23 18:29:29.329 D/BackupManagerService( 869): Calling doFullBackup() on com.viber.voip
03-23 18:29:29.337 V/BackupServiceBinder(10713): doFullBackup() invoked
03-23 18:29:29.342 I/file_backup_helper(10713): Name: apps/com.viber.voip/r/app_webview
03-23 18:29:29.343 I/file_backup_helper(10713): Name: apps/com.viber.voip/r/app_webview/GPUCache
03-23 18:29:29.344 I/file_backup_helper(10713): Name: apps/com.viber.voip/r/app_webview/GPUCache/index-dir
03-23 18:29:29.345 I/file_backup_helper(10713): Name: apps/com.viber.voip/r/app_webview/GPUCache/index-dir/the-real-index
03-23 18:29:29.346 I/file_backup_helper(10713): Name: apps/com.viber.voip/r/app_webview/GPUCache/index
03-23 18:29:29.347 I/file_backup_helper(10713): Name: apps/com.viber.voip/r/app_webview/Local Storage
03-23 18:29:29.367 I/file_backup_helper(10713): Name: apps/com.viber.voip/r/app_webview/Local Storage/https_account.viber.com_0.localstorage-journal
03-23 18:29:29.368 I/file_backup_helper(10713): Name: apps/com.viber.voip/r/app_webview/Local Storage/https_account.viber.com_0.localstorage
03-23 18:29:29.369 I/file_backup_helper(10713): Name: apps/com.viber.voip/r/app_webview/Local Storage/http_market.viber.com_0.localstorage-journal
03-23 18:29:29.370 I/file_backup_helper(10713): Name: apps/com.viber.voip/r/app_webview/Local Storage/http_market.viber.com_0.localstorage
03-23 18:29:29.371 I/file_backup_helper(10713): Name: apps/com.viber.voip/r/app_webview/Cookies-journal
03-23 18:29:29.371 I/file_backup_helper(10713): Name: apps/com.viber.voip/r/app_webview/Web Data-journal
03-23 18:29:29.389 I/file_backup_helper(10713): Name: apps/com.viber.voip/r/app_webview/Cookies
03-23 18:29:29.390 I/file_backup_helper(10713): Name: apps/com.viber.voip/r/app_webview/Web Data
03-23 18:29:29.430 I/file_backup_helper(10713): Name: apps/com.viber.voip/r/app_webview/paks

without the parameters the file is 26byte and the logcat is almost the same

03-23 18:55:26.441 D/BackupManagerService( 869): Binding to full backup agent : com.viber.voip
03-23 18:55:26.492 I/ActivityManager( 869): Start proc com.viber.voip for backup android/FullBackupAgent: pid=15227 uid=10159 gids={50159, 9997, 3003, 1028, 1015, 3002, 3001} abi=armeabi-v7a
03-23 18:55:26.495 D/BackupManagerService( 869): awaiting agent for ApplicationInfo{301a383b com.viber.voip}
03-23 18:55:26.695 D/BackupManagerService( 869): agentConnected pkg=com.viber.voip agent=android.os.BinderProxy@1fc6a4b1
03-23 18:55:26.695 I/BackupManagerService( 869): got agent android.app.IBackupAgent$Stub$Proxy@1fa83d96
03-23 18:55:26.701 I/BackupRestoreController( 869): Getting widget state for user: 0
03-23 18:55:26.708 I/file_backup_helper( 869): Name: apps/com.viber.voip/_manifest
03-23 18:55:26.709 D/BackupManagerService( 869): Calling doFullBackup() on com.viber.voip
03-23 18:55:26.713 V/BackupServiceBinder(15227): doFullBackup() invoked
03-23 18:55:26.722 I/file_backup_helper(15227): Name: apps/com.viber.voip/r/app_webview
03-23 18:55:26.727 I/file_backup_helper(15227): Name: apps/com.viber.voip/r/app_webview/GPUCache
03-23 18:55:26.728 I/file_backup_helper(15227): Name: apps/com.viber.voip/r/app_webview/GPUCache/index-dir
03-23 18:55:26.729 I/file_backup_helper(15227): Name: apps/com.viber.voip/r/app_webview/GPUCache/index-dir/the-real-index
03-23 18:55:26.730 I/file_backup_helper(15227): Name: apps/com.viber.voip/r/app_webview/GPUCache/index
03-23 18:55:26.736 I/file_backup_helper(15227): Name: apps/com.viber.voip/r/app_webview/Local Storage
03-23 18:55:26.736 I/file_backup_helper(15227): Name: apps/com.viber.voip/r/app_webview/Local Storage/https_account.viber.com_0.localstorage-journal
03-23 18:55:26.737 I/file_backup_helper(15227): Name: apps/com.viber.voip/r/app_webview/Local Storage/https_account.viber.com_0.localstorage
03-23 18:55:26.737 I/file_backup_helper(15227): Name: apps/com.viber.voip/r/app_webview/Local Storage/http_market.viber.com_0.localstorage-journal
03-23 18:55:26.737 I/file_backup_helper(15227): Name: apps/com.viber.voip/r/app_webview/Local Storage/http_market.viber.com_0.localstorage
03-23 18:55:26.738 I/file_backup_helper(15227): Name: apps/com.viber.voip/r/app_webview/Cookies-journal
03-23 18:55:26.738 I/file_backup_helper(15227): Name: apps/com.viber.voip/r/app_webview/Web Data-journal
03-23 18:55:26.740 I/file_backup_helper(15227): Name: apps/com.viber.voip/r/app_webview/Cookies
03-23 18:55:26.741 I/file_backup_helper(15227): Name: apps/com.viber.voip/r/app_webview/Web Data
03-23 18:55:26.762 I/file_backup_helper(15227): Name: apps/com.viber.voip/r/app_webview/paks

So if anybody is able help you, I hope that can help me too! :cool: