[cifs-protocol] Windows 10 backup failing against Samba

Uri Simchoni uri at samba.org
Tue Feb 23 20:04:40 UTC 2016

Hi Bryan,

Continuing the discussion from samba-technical.

We have a Windows 10 VM (details attached) failing to create a system 
image on a Samba 4.3.4 server share. We would like to understand the 
root cause so that a fix can be supplied.

To reproduce:
1. Setup a stand-alone Samba-based file server as per 

(I basically used the Fedore FC23 build, with a minimal smb.conf as 
listed in the wiki, and an ext4 file system. had do disable selinux to 
avoid frustration. But it should behave the same on other builds)

2. On a Win10 machine, create a system image using wbadmin command line, 
as listed in attached cmd.txt session

After snapshot creation phase, the operation fails with "incorrect 
function" error message.

info.txt - basic details on the client OS
cmd.txt - capture of the wbadmin command and output
backup.pcap - packet capture of the SMB3 session

The packet capture shows an attempt to open the .vhdx with
SVHDX_OPEN_DEVICE_CONTEXT, which returns this error.

If my reading of [MS-SMB2] is correct, then Samba is in compliance here, 
since it does not support shared VHDX.

It's not entirely clear how/whether the client is supposed to test for 
support of SVHDX - I'm waiting to get my hands on a Server 
2012R2/2016TP4 to compare. In an SDC presentation from 2013 it says the 
existence of an alternate data stream is the test, I see no such test in 
the packet capture.

Please advise.

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Host Name:                 DESKTOP-610P64R
OS Name:                   Microsoft Windows 10 Pro
OS Version:                10.0.10586 N/A Build 10586
OS Manufacturer:           Microsoft Corporation
OS Configuration:          Standalone Workstation
OS Build Type:             Multiprocessor Free
Registered Owner:          qa
Registered Organization:   
Product ID:                00331-10000-00001-AA457
Original Install Date:     11/27/2015, 5:15:18 AM
System Boot Time:          2/21/2016, 1:48:06 AM
System Manufacturer:       Microsoft Corporation
System Model:              Virtual Machine
System Type:               x64-based PC
Processor(s):              1 Processor(s) Installed.
                           [01]: Intel64 Family 6 Model 44 Stepping 2 GenuineIntel ~2926 Mhz
BIOS Version:              American Megatrends Inc. 090006 , 5/23/2012
Windows Directory:         C:\WINDOWS
System Directory:          C:\WINDOWS\system32
Boot Device:               \Device\HarddiskVolume1
System Locale:             en-us;English (United States)
Input Locale:              en-us;English (United States)
Time Zone:                 (UTC-08:00) Pacific Time (US & Canada)
Total Physical Memory:     3,072 MB
Available Physical Memory: 1,946 MB
Virtual Memory: Max Size:  3,584 MB
Virtual Memory: Available: 2,308 MB
Virtual Memory: In Use:    1,276 MB
Page File Location(s):     C:\pagefile.sys
Domain:                    WORKGROUP
Logon Server:              \\DESKTOP-610P64R
Hotfix(s):                 9 Hotfix(s) Installed.
                           [01]: KB3116900
                           [02]: KB3116908
                           [03]: KB3120677
                           [04]: KB3122947
                           [05]: KB3124200
                           [06]: KB3124262
                           [07]: KB3124263
                           [08]: KB3135173
                           [09]: KB3135782
Network Card(s):           2 NIC(s) Installed.
                           [01]: TAP-Windows Adapter V9
                                 Connection Name: Ethernet 2
                                 Status:          Media disconnected
                           [02]: Microsoft Hyper-V Network Adapter
                                 Connection Name: Ethernet
                                 DHCP Enabled:    Yes
                                 DHCP Server:
                                 IP address(es)
                                 [02]: fe80::707d:d94b:ae92:fb14
Hyper-V Requirements:      A hypervisor has been detected. Features required for Hyper-V will not be displayed.
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C:\WINDOWS\system32>wbadmin start backup -allCritical -backupTarget:\\\ush -user:localu1 -password:password00
wbadmin 1.0 - Backup command-line tool
(C) Copyright 2013 Microsoft Corporation. All rights reserved.

Note: The backed up data cannot be securely protected at this destination.
Backups stored on a remote shared folder might be accessible by other
people on the network. You should only save your backups to a location
where you trust the other users who have access to the location or on a
network that has additional security precautions in place.

Retrieving volume information...
This will back up System Reserved (500.00 MB),(C:) to \\\ush.
Do you want to start the backup operation?
[Y] Yes [N] No y

The backup operation to \\\ush is starting.
Creating a shadow copy of the volumes specified for backup...
Creating a shadow copy of the volumes specified for backup...
Creating a shadow copy of the volumes specified for backup...
Creating a shadow copy of the volumes specified for backup...
The backup of volume System Reserved (500.00 MB) could not be completed. Error: Incorrect function.
Summary of the backup operation:

The backup operation stopped before completing.
The backup operation stopped before completing.
Detailed error: Incorrect function.
Log of files successfully backed up:

Log of files for which backup failed:

There was a failure in preparing the backup image of one of the volumes in the backup set.
Incorrect function.

C:\WINDOWS\system32>type c:\Windows\Logs\WindowsBackup\Backup_Error-23-02-2016_14-31-49.log
Backup of volume \\?\Volume{1948156d-0000-0000-0000-100000000000}\ has failed. Incorrect function.

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