The /v/qn parameter is actually a combination of two distinct MSI installation switches passed through Windows Installer (msiexec.exe). Here's the breakdown:

• /v: Indicates that subsequent parameters should be passed to the MSI engine
• /qn: Sets the UI level to "no UI" (completely silent installation)

This syntax originates from how InstallShield wraps MSI installations. The forward slash format (/v/qn) is necessary because:

setup.exe /s /v"/qn"  # This is the proper canonical form
setup.exe /s /v/qn    # Commonly used shorthand

The space-separated version (/v /qn) fails because the MSI parser expects the entire parameter string after /v to be quoted.

Different installers may require slight variations:

# For pure MSI installations (using msiexec directly):
msiexec /i package.msi /qn

# InstallShield wrapped installers:
setup.exe /s /v"/qn"

# Some vendors might require uppercase:
SETUP.EXE /S /V"/QN"

Here's how to implement silent installations in different scenarios:

# PowerShell script example:
Start-Process -FilePath "setup.exe" -ArgumentList "/s /v"/qn REBOOT=ReallySuppress"" -Wait

# Batch file implementation:
@echo off
setup.exe /s /v"/qn REBOOT=ReallySuppress"

If /v/qn isn't working as expected, try these alternatives:

• Check vendor documentation for specific silent install requirements
• Try the standard MSI parameters directly: msiexec /i package.msi /quiet /norestart
• Use logging to diagnose issues: /v"/qn /l*v install.log"

Remember that some installers may have custom implementations that override standard MSI behavior.

When working with Windows Installer packages (MSI), you'll often encounter command-line parameters like /s /v"/qn" for silent installations. The /v prefix might seem confusing at first glance, but it serves a specific purpose in MSI execution.

The complete syntax actually consists of two parts:

msiexec /i package.msi /s /v"/qn"

• /s - Typically the silent switch for the outer installer (often InstallShield)
• /v - Signals that what follows should be passed to the Windows Installer service (msiexec)
• /qn - The actual Windows Installer quiet mode parameter

The /v"" syntax is necessary because some setup executables act as wrappers around MSI packages. The parameters inside the quotes after /v get forwarded to msiexec. This explains why /v /qn (with space) fails - it breaks the parameter passing mechanism.

Different installer technologies handle this differently:

// InstallShield example
setup.exe /s /v"/qn"

// Wise Installer example
setup.exe /s /qn

// NSIS example
setup.exe /S

For MSI packages directly:

msiexec /i "MyApp.msi" /qn /norestart

For wrapped installers:

setup.exe /s /v"/qn REBOOT=ReallySuppress"

Combine with other msiexec parameters:

/l*v "install.log"  - Detailed logging
REBOOT=ReallySuppress - Prevent reboots
INSTALLDIR="C:\Path" - Custom install location