full adb backup not creating .ab file for Realme 2 Pro

Question

I am unable to create a full phone backup file of my Realme 2 Pro (model RMX1801) through the ADB. The phone runs stock ColorOS 7 (Android 10). The device is not rooted and I do not want to root it. Doing that would delete my data. Also, my device hasn't had any screen-lock protection days before I ran the very first command (which is several hours amounting to few days before the original-revision of this post) and remaining wholly unchanged to the best of my knowledge till the timestamp of latest-revision.

Here's what I've tried. I launched Command prompt (cmd.exe) and ran:

C:\Users\Dell> OneDrive\Desktop\adb.exe
C:\Users\Dell> adb devices
List of devices attached
86b3470 device

At this point I started to take backup. I have tried a couple of things and I'm categorizing them now.

Attempts when I entered no backup-encryption key whatsoever

C:\Users\Dell>adb backup -all -f -nosystem C:\Users\Dell\OneDrive\Documents\RMX1801backup.ab 
C:\Users\Dell>adb backup -all -f -nosystem -shared C:\Users\Dell\OneDrive\Documents\RMX1801backup.ab

Both of the commands showed on the UI that backup was taking place. But none of them created the backup file in my PC.

Attempts when I entered a backup-encryption key

C:\Users\Dell>adb backup -all -f -nosystem C:\Users\Dell\OneDrive\Documents\RMX1801backup.ab
C:\Users\Dell>adb backup -all -f -nosystem -shared C:\Users\Dell\OneDrive\Documents\RMX1801backup.ab

No change, whatsoever.

I also changed the destination path from OneDrive/Documents to OneDrive/Desktop and repeated all the above commands. That did not work either.

Attempts with double-quotes

C:\Users\Dell>adb backup "-f -all -nosystem C:\Users\Dell\OneDrive\Desktop\RMX1801backup.ab"    
C:\Users\Dell>adb backup "-f -all -nosystem -shared C:\Users\Dell\OneDrive\Desktop\RMX1801backup.ab"

Did not work.

Changed double quotes position

C:\Users\Dell>adb backup "-f -all -nosystem" C:\Users\Dell\OneDrive\Documents\RMX1801backup.ab
C:\Users\Dell>adb backup "-f -all -shared -nosystem" C:\Users\Dell\OneDrive\Documents\RMX1801backup.ab
C:\Users\Dell>adb backup -f "-all -nosystem -shared" C:\Users\Dell\OneDrive\Desktop\RMX1801backup.ab
C:\Users\Dell>adb backup -f "-all -nosystem -shared" C:\Users\Dell\OneDrive\Desktop\RMX1801backup.ab

Here's what happened in the case of double-quoted commands: All of the ones ending the double-quotes before the backup file's path appeared to have started the backup process but it did not create the backup file either. The duration of the backup process in the UI was also incredibly shorter, aka literally instantaneous, in these attempts.

---

As asked in the comments, the versions of adb are produced below:

C:\Users\Dell>adb version
Android Debug Bridge version 1.0.41
Version 33.0.3-8952118
Installed as C:\Users\Dell\OneDrive\Desktop\platform-tools\adb.exe

C:\Users\Dell>adb shell adbd --version
* daemon not running; starting now at tcp:5037
* daemon started successfully
/system/bin/sh: adbd: inaccessible or not found

C:\Users\Dell>adb devices
List of devices attached
86b3470 device    

C:\Users\Dell>adb shell
RMX1801:/ $ adbd --version
/system/bin/sh: adbd: inaccessible or not found
127|RMX1801:/ $

here are the [hitherto] unsolicited screencaps/screengrabs/screenshots:

Answer 1

adb help specifies usage of backup

  adb backup [-f <file>] [-apk|-noapk] [-shared|-noshared] [-all] [-system|-nosystem] [<packages...>]
                               - write an archive of the device's data to <file>.
                                 If no -f option is supplied then the data is written
                                 to "backup.ab" in the current directory.
                                 (-apk|-noapk enable/disable backup of the .apks themselves
                                    in the archive; the default is noapk.)
                                 (-shared|-noshared enable/disable backup of the device's
                                    shared storage / SD card contents; the default is noshared.)
                                 (-all means to back up all installed applications)
                                 (-system|-nosystem toggles whether -all automatically includes
                                    system applications; the default is to include system apps)
                                 (<packages...> is the list of applications to be backed up.  If
                                    the -all or -shared flags are passed, then the package
                                    list is optional.  Applications explicitly given on the
                                    command line will be included even if -nosystem would
                                    ordinarily cause them to be omitted.)

according to usage the [-f <file>] parameter requires second argument <file> which is missing on your command:

adb backup -all -f -nosystem C:\Users\Dell\OneDrive\Documents\RMX1801backup.ab

correct usage with 2nd argument:

adb backup -f C:\Users\Dell\OneDrive\Documents\RMX1801backup.ab -all -nosystem

Note: full backup is not possible with adb. only apps with android:allowBackup=true in AndroidManifest.xml can be backed up with adb.

one can make test if adb backup is working at all with single package that allows backup, such as Chrome Browser which comes preinstalled on most devices.

example:

adb backup com.android.chrome

this will create backup.ab containing Chrome Browser app data. the location of the file is the current directory.