AppRollback vs NasRollback -> ComponentMode - am I on the right track?

[smanross]

Howdy, I've been using AlphaVSS for a few months now, and using AppRollback context, and wanted to change to using NasRollBack context, as I believe this will give me a snapshot set in a read only state, where the files won't update on the snapshot.ExposedName after I take the initial snapshot, and then I can start backing up the files to another drive on the system with a point in time recovery model.

• Hopefully, that makes sense, and is true.

After trying to use a NasRollback context in the provider, I started getting an error suggesting I've done something wrong.

Error after runnig PrepareForBackup()

VssBadStateException: The VSS object was in an incorrect state for the requested operation.
   at Alphaleonis.Win32.Vss.VssBackupComponents.PrepareForBackup() in C:\Repos\AlphaVSS\src\AlphaVSS.Platform\VssBackupComponents.cpp:line 518

In troubleshooting this, I started looking at the ComponentMode and the various components.

my code is based off of your great samples...
https://github.com/alphaleonis/AlphaVSS-Samples/blob/develop/src/VssBackup/VssBackup.cs

Python code:

import alphavss # a python class that I've wrapped the python .NET code for AlphaVSS in
# AppRollback works, and NasRollback doesn't work
# provider = alphavss.VSSProvider(operation='backup', context=alphavss.constants.AppRollback, debug=True)
provider = alphavss.VSSProvider(operation='backup', context=alphavss.constants.NasRollback, debug=True)

cmp = provider.create_backup_components() # function I encapsulated your methods into
cmp.InitializeForBackup(None)
cmp.GatherWriterMetadata()

for writer in cmp.WriterMetadata:
    print(writer.WriterName)
    for component in writer.Components:
        print("\t", component.ComponentName)
        for filedescriptor in component.Files:
            print(f'\t\tpath: {filedescriptor.Path} -- FileSpecification: {filedescriptor.FileSpecification}')

In this exercise, I think I've found the problem (maybe), and wanted to ask if you might see if I am going in the right direction or not.

Namely the ASR writer includes data for every volume in my system and the 3 hard drives (of which, I am excluding one drive and one volume from the snapshot operation because I am copying the C, D and F drives to the G drive in my code):

# snippet of output from for loop above:
ASR Writer
         ASR
         Volume{guid1}
         Volume{guid2}
         Volume{guid3}
         Volume{guid4}
         Volume{guid5}   < --- G Drive
         harddisk5
         harddisk0
         harddisk6  < --- G Drive
         BCD
                path: \\?\Volume{guid1}\Boot -- FileSpecification: *.*

I'm assuming that I need to set ComponentMode = True and exclude "harddisk6" and "Volume{guid5}" from the components I want to enable in order to enable NasRollback context since I don't want to make a complete backup of the system, and exclude the G Drive in this process.

If all this is correct, it looks like I am adding code to "Examine Components" that I need and exclude the volumes/drives I am not including in the backup set via:.

cmp.AddComponent(
    instanceId,
    writerId,
    componentType,
    logicalPath,
    componentName,
)
Docstring:      Void AddComponent(System.Guid, System.Guid, Alphaleonis.Win32.Vss.VssComponentType, System.String, System.String)

Thanks for the long read. And Thanks for the .NET code that makes sense of all this so I could try to port this to Python.NET!

Please let me know if I am on the right track. :)

Steven