When managing production Hyper-V environments, the traditional shutdown-and-copy approach causes unacceptable downtime. Microsoft's Volume Shadow Copy Service (VSS) provides the solution through disk shadow copies - but implementing it via command line requires precise syntax.

1. Diskshadow.exe (built into Windows Server)
2. VSS-aware Hyper-V integration services
3. Target storage (local disk or UNC path)
4. Administrator privileges

Here's the minimal diskshadow script to snapshot running VMs:

set context persistent
set verbose on
begin backup
add volume C: alias SystemVolume
add volume E: alias VMStorage
create
expose %SystemVolume% Z:
expose %VMStorage% Y:
exec "C:\scripts\robocopy_backup.bat"
end backup

This complete solution handles multiple VMs with verification:

:: diskshadow_script.txt
set metadata C:\backups\vss_meta.cab
set context persistent
begin backup
add volume C: alias SystemDrive
add volume F: alias VM_Cluster
create
expose %SystemDrive% S:
expose %VM_Cluster% V:

:: Robocopy the exposed shadow copies
exec "cmd /c robocopy V:\VM01 D:\backups\VM01 /MIR /R:1 /W:1 /NP /TEE /LOG+:C:\logs\vm01_backup.log"
exec "cmd /c robocopy V:\VM02 D:\backups\VM02 /MIR /R:1 /W:1 /NP /TEE /LOG+:C:\logs\vm02_backup.log"

:: Verify VSS integrity
exec "cmd /c vssadmin list shadows /for=F: > C:\logs\vss_verify.log"

end backup

Persistent context: Maintains the shadow copy beyond command execution

Alias naming: Required for subsequent volume exposure

Robocopy switches: /MIR mirrors directory trees, /R/W control retries

:: Add to your batch file:
if %ERRORLEVEL% NEQ 0 (
   echo Backup failed at %TIME% >> C:\logs\backup_errors.log
   diskshadow /s C:\scripts\cleanup.txt
   exit /b 1
)

When targeting UNC paths:

net use Z: \\backup_server\share /USER:backup_agent P@ssw0rd /PERSISTENT:YES
robocopy V:\VM01 Z:\hyperv_backups\VM01 /ZB /MIR /COPYALL

Create a scheduled task with these actions:

1. Program: diskshadow.exe
2. Arguments: /s C:\scripts\diskshadow_script.txt
3. Run as: SYSTEM account
4. Triggers: Daily at 2AM
5. Conditions: Start only if network available

Backing up running Hyper-V VMs without downtime is crucial for production environments. The built-in Windows Volume Shadow Copy Service (VSS) combined with diskshadow.exe provides a robust CLI approach that's scriptable and reliable.

1. VSS Writers: Hyper-V VSS writer coordinates VM snapshots
2. Diskshadow.exe: Microsoft's VSS requester tool with scripting capabilities
3. Storage: Local disk or SMB share for backup destination

@echo off
set BACKUP_DIR=\\backupserver\vmbackups
set VM_NAME=ProdServer2019

diskshadow.exe /s backup_script.txt
robocopy C:\ClusterStorage\Volume1\ %BACKUP_DIR%\%VM_NAME%_%DATE% /MIR /ZB /R:1 /W:1 /LOG:%BACKUP_DIR%\%VM_NAME%.log

Corresponding diskshadow script (backup_script.txt):

set context persistent
set verbose on
begin backup
add volume C: alias SystemVolume
add volume D: alias VMStorage
create
expose %SystemVolume% S:
expose %VMStorage% V:
end backup

• Run as Administrator with elevated privileges
• Ensure Hyper-V Integration Services are updated in VMs
• Test restore procedures regularly
• Monitor VSS writer health with vssadmin list writers

For multiple VMs with error handling:

powershell.exe -Command {
    $vms = Get-VM | Where-Object {$_.State -eq 'Running'}
    foreach ($vm in $vms) {
        try {
            $backupName = "$($vm.Name)_$(Get-Date -Format 'yyyyMMddHHmm')"
            diskshadow.exe /s "C:\scripts\$backupName.dsh"
            Export-VM -Name $vm.Name -Path "\\backupnas\vmexports\$backupName"
        }
        catch {
            Write-EventLog -LogName Application -Source "HyperVBackup" -EntryType Error -EventId 500 -Message $_.Exception.Message
        }
    }
}

VSS_E_WRITERERROR: Check application logs in VMs and restart VSS service
Insufficient storage: Implement pre-backup size checks with PowerShell's Get-Volume
Access denied: Configure proper share permissions and firewall rules for SMB