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I have an old droid RAZR Maxx (4.1.2) that I decided I want to root, but I want to make a backup first just in case. I've followed instructions from this site:

How To Create a Full Android Phone or Tablet Backup Without Rooting or Unlocking Your Device

My command was this:

adb backup -apk -shared -all -f c:\backup.ab

The resulting backup.ab file on the C: drive was only 41 bytes and, when opened in a hex editor, appears to only be the header of the backup file. I'm wondering what I'm doing wrong here, I've googled but can't find anything that helps. Any suggestions?

Edit: This is not a duplicate of the suggested a topic linked by beeshyams. That topic explains why the user couldn't back up one single app's files, I'm trying to back up everything. I don't care if I don't get SMS included in that backup because it's an old phone, I'm not using it to text, but there are other apps and settings that should back up without issue.

xavier_fakerat
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HaLo2FrEeEk
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    Search [tag:adb] tag (added to your question), duplicate of http://android.stackexchange.com/q/114437/131553 – beeshyams Apr 26 '16 at 06:26
  • It's not a duplicate, I'm not asking how to just back up SMS/MMS, but the entire phone. Apps, settings, files, etc. I've tried this on two different Motorola phones now with the same result (the other one was a droid ultra). – HaLo2FrEeEk Apr 26 '16 at 06:29
  • It doesn't explain why a requested backup of the entire system results in a 41 byte file, it explains why the backup of a single app does, so it doesn't answer my question. – HaLo2FrEeEk Apr 26 '16 at 06:36
  • See this, if it still doesn't address, quote this in your question and amplify – beeshyams Apr 26 '16 at 06:43
  • That answer literally says to do exactly what my question says I did. I've got the path to adb on my environment variables so I click start, type "cmd" type "adb devices" to make sure my phone is connected properly (which it is), then I type the backup command and I get a 41 byte file, every time. I'm not worried about backing up calendar, contacts or SMS data, but there's nothing about the entire thing failing because those apps can't be backed up. – HaLo2FrEeEk Apr 26 '16 at 07:41
  • Can you try making a backup of a single app and see if you still end up with only header information? Try with an app which doesn't disallow backup, such Firefox or ES File Explorer. – Firelord Apr 26 '16 at 18:23
  • I will try that and add a comment in a minute, but I thought I should note here that I rooted the device last night and I still can't get the backup to work. I've verified that I have root access, I do, but the backup still results in a 41 byte file. I'll comment with my results of a single app. – HaLo2FrEeEk Apr 26 '16 at 23:32
  • Ok, I tested. I'm not 100% sure the command was right, I can't find a ton of documentation on the backup command, but I used this: adb backup -f C:\esbackup.ab com.estrongs.android.pop and I still got a 41 byte file. I tried this command too: adb backup -shared -f C:\testbackup.ab with the same results. Seems my phone just doesn't want to do a stupid backup! – HaLo2FrEeEk Apr 26 '16 at 23:41
  • Consider using @ followed by user's name to notify them, such as @Firelord, else the user would not be notified of your followup comment. Now, could you try this command: adb shell bu backup com.estrongs.android.pop > C:\es_new_backup.ab and see if it still causes a 41 bytes file? If the issue persist, please have a new terminal/console running adb logcat and in another one, issue your app specific adb backup command and observe errors or anything in logcat's output. You may as well share the output with us too. – Firelord Apr 27 '16 at 12:38
  • I'm facing with a similar issue, and, for example, Helium Backup complains for an application that is disallowed to be backed up. This might be related to your question as well: http://android.stackexchange.com/questions/68209/what-is-the-purpose-of-an-app-disallowing-backups-androidallowbackup-false – Lyubomyr Shaydariv Jul 06 '16 at 05:50

2 Answers2

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Found solution here, worked for me:

https://docs.j7k6.org/android-adb-backup-41-bytes-549-bytes-bug-fix/

Appearantly the adb backup command stopped working for older Android devices in recent versions of the Android Debug Bridge. When invoking a backup with adb, the backup process is started but stops immediately, leaving a local backup.ab file with a filesize of only 49 bytes (549 bytes when the backup is encrypted with a password). This bug is well known, but hasn’t been fixed at least until recently (version 1.0.39). To fix this behaviour, download the last working version of the adb executable (1.0.31) and invoke the backup with this. The executables for all platforms can be downloaded at Mozilla.

https://archive.mozilla.org/pub/labs/android-tools/

adb-1.0.31-linux.zip    479K    09-Sep-2015 18:44
adb-1.0.31-linux64.zip  455K    09-Sep-2015 18:44
adb-1.0.31-mac.zip  433K    09-Sep-2015 18:44
adb-1.0.31-windows.zip  474K    09-Sep-2015 18:44

Download, unzip, run unzipped adb:

(linux, mac)

./adb devices
./adb backup -apk -shared -all -f backup-file.adb

(win)

adb devices
adb backup -apk -shared -all -f backup-file.adb

Enjoy! ;)

user3439968
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    Does this only work with -all? I'm trying adb backup -noapk com.android.chrome with version 1.0.40 and I still get the 549 bytes file.. – thomasa88 Mar 24 '19 at 07:00
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    I tried with 1.0.31 but it does not make the backup prompt appear on my phone. Android 8.0.0. – thomasa88 Mar 24 '19 at 07:11
  • @thomasa88, quote from answer:"Appearantly the adb backup command stopped working for older Android devices". Android 8.0.0 is prelast version of android on 04.2019. adb-1.0.31 I use for android 4... For newer(8.0.0) version of android try use newer versions of adb. – user3439968 Apr 15 '19 at 22:10
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You should not try to backup the "entire" phone with adb, because it's plenty of bugs. My recommendation is to backup apps one by one and avoid the '-shared' flag because backup of shared storage is broken. Just copy and paste to a memory card of use ftp server to upload to your computer those things from internal sdcard.

Again: backup one app at a time and check for .ab file size so it's not "empty". It will be empty when the unencrypted backup has 41, 47 or 49 byte size. If encrypted will be 549 byte size for empty.

Latest adb is 1.0.41

Note also that some apps don't allow adb backup, and other even if allow it don't "store" anything on there because of app policy. Examples are apps which use cloud services like Google, etc.

Smeterlink
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