Complete IIS and Windows Environment Variables Knowledge Base
Windows Environment Variables Reference
What are Environment Variables?
Environment variables are system-defined values that programs use to find files and folders regardless of which drive Windows is installed on or how the system is configured.
System Location Variables
%windir%= Windows directory (usually C:\Windows)%SystemRoot%= Same as %windir% (C:\Windows)%SystemDrive%= Drive where Windows is installed (C:)%System32%= System32 folder (C:\Windows\System32)%ProgramFiles%= Program Files folder (C:\Program Files)%ProgramFiles(x86)%= 32-bit programs on 64-bit systems (C:\Program Files (x86))%ProgramData%= Shared application data (C:\ProgramData)%CommonProgramFiles%= Shared program files (C:\Program Files\Common Files)%CommonProgramFiles(x86)%= 32-bit shared files (C:\Program Files (x86)\Common Files)
User Profile Variables
%UserProfile%= Current user's home folder (C:\Users\YourName)%HomeDrive%= Drive containing user profiles (C:)%HomePath%= Path to user profile (\Users\YourName)%AppData%= User's roaming application data (C:\Users\YourName\AppData\Roaming)%LocalAppData%= Local app data (C:\Users\YourName\AppData\Local)%Temp%= Temporary files folder (C:\Users\YourName\AppData\Local\Temp)%TMP%= Same as %Temp%%Desktop%= User's desktop (C:\Users\YourName\Desktop)%Documents%= User's documents (C:\Users\YourName\Documents)%StartMenu%= User's start menu (C:\Users\YourName\AppData\Roaming\Microsoft\Windows\Start Menu)%Startup%= User's startup folder (C:\Users\YourName\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup)
System Information Variables
%ComputerName%= Your computer's name%UserName%= Currently logged in user%UserDomain%= Domain name (if joined to a domain)%UserDnsDomain%= DNS domain name%LogonServer%= Domain controller that authenticated the user%ProcessorArchitecture%= CPU type (AMD64, x86, ARM64)%ProcessorIdentifier%= Detailed CPU information%ProcessorLevel%= CPU family%ProcessorRevision%= CPU revision%Number_of_Processors%= Number of CPU cores
Network and Domain Variables
%ComputerName%= Local computer name%UserDomain%= Logon domain%LogonServer%= Domain controller name%UserDnsDomain%= DNS domain name
Development and System Variables
%Path%= System PATH variable (directories searched for executables)%PathExt%= File extensions considered executable (.exe, .bat, .cmd, etc.)%OS%= Operating system name (Windows_NT)%Processor_Architecture%= Processor architecture%Random%= Random number between 0 and 32767%Time%= Current time%Date%= Current date%CD%= Current directory%CmdCmdLine%= Command line used to start cmd.exe
Special Shared Folders
%Public%= Public user folder (C:\Users\Public)%AllUsersProfile%= All users data (C:\ProgramData)%CommonStartMenu%= Shared start menu (C:\ProgramData\Microsoft\Windows\Start Menu)%CommonStartup%= Shared startup folder (C:\ProgramData\Microsoft\Windows\Start Menu\Programs\StartUp)%CommonDesktop%= Shared desktop (C:\Users\Public\Desktop)%CommonDocuments%= Shared documents (C:\Users\Public\Documents)
How to View Environment Variables
Command Prompt:
set # Show all variables
echo %windir% # Show specific variable
set windir # Show variables starting with "windir"
PowerShell:
Get-ChildItem Env: # Show all variables
$env:windir # Show specific variable
$env:windir = "C:\Windows" # Set variable
Windows GUI:
- Press Win + R, type sysdm.cpl, press Enter
- Click "Advanced" tab → "Environment Variables" button
Why Use Environment Variables?
- Portability: Scripts work on any Windows system regardless of drive configuration
- Flexibility: Programs find files even if Windows is installed to different drives
- Maintenance: Easier to update paths centrally
- Security: Avoid hardcoding sensitive paths in scripts
IIS Knowledge Base Guide
Why Install IIS on F: Drive Instead of C:
Performance Benefits
- Separates web content from system drive to reduce I/O contention
- F: drive is typically larger storage dedicated to data
- C: drive reserved for operating system files
Management Advantages
- Easier backup strategies - web content isolated from system files
- Better security through application separation
- Corporate policies often mandate separating applications from OS
- Storage management - prevents web logs from filling system drive
IIS Manager vs Log Files
IIS Manager
What it is: Graphical management console for configuring IIS
- Configure websites, application pools, virtual directories
- Set authentication, SSL certificates, URL rewriting rules
- Monitor real-time performance and active connections
- Location: %windir%\system32\inetsrv\InetMgr.exe
IIS Log Files
What they are: Automatically generated records of all web requests
- Default location: %SystemDrive%\inetpub\logs\LogFiles\W3SVC1\
- Contains request details, response codes, timestamps, IP addresses
- Used for traffic analysis, troubleshooting, security monitoring, compliance
W3C Log Format - Why Use It?
Industry Standard
- W3C Extended Log Format is universally recognized
- Compatible with most log analysis tools (LogParser, AWStats, Webalizer)
Customizable and Efficient
- Choose which fields to log (date, IP, status codes, user agents, etc.)
- Only logs necessary data, reducing file size and storage costs
- Well-structured format enables automated parsing and analysis
Tool Integration
- Works seamlessly with Microsoft LogParser
- Supports third-party analytics and monitoring solutions
- Easy to import into databases and reporting tools
IIS Server Configuration Options
.NET Authorization
Purpose: Controls access to .NET applications and resources
What it manages:
- Authentication methods (Windows Authentication, Forms Authentication, Anonymous)
- Authorization rules for specific users and roles
- Access control for pages, directories, or application methods
- Integration with ASP.NET membership providers and Active Directory
.NET Compilation
Purpose: Defines how ASP.NET code is compiled and executed
Key settings:
- Debug vs Release mode: Debug includes debugging symbols, Release is optimized for performance
- Target Framework: Specifies .NET version (.NET Framework 4.8, .NET Core, etc.)
- Compilation options: Batch compilation settings for better performance
- Temporary files: Manages compiled assemblies in temporary ASP.NET files directory
.NET Error Pages
Purpose: Controls how application errors are displayed to users
Configuration options:
- Custom error pages: Display user-friendly pages instead of technical stack traces
- Error modes:
- On - Always show custom errors
- Off - Always show detailed errors (development only)
- RemoteOnly - Show custom errors to remote users, detailed to local users
- Default redirects: Specify custom pages for 404 (not found) and 500 (server error) responses
- Security benefit: Prevents sensitive application information from being exposed to end users
MIME Types
Purpose: Tells web browsers how to handle different file types
How it works:
- File associations: Maps file extensions to content types
- .pdf → application/pdf
- .jpg → image/jpeg
- .json → application/json
- Browser behavior: Determines whether file is displayed in browser or downloaded
- Content handling: Controls streaming, caching, and compression settings
- Security: Prevents execution of unknown or potentially dangerous file types
Common MIME types:
- text/html - HTML web pages
- text/css - Cascading Style Sheets
- application/javascript - JavaScript files
- image/png - PNG image files
- application/json - JSON data responses
- application/octet-stream - Generic binary files (forces download)
IIS Environment Variables
%SystemDrive%\inetpub\wwwroot- Default website root%SystemDrive%\inetpub\logs\LogFiles- Default log location%windir%\system32\inetsrv- IIS binaries and tools%ProgramFiles%\IIS- IIS program files (if installed)
Quick Reference Commands
Check Environment Variables
echo %windir% # Windows directory
echo %SystemDrive% # System drive
echo %UserProfile% # User profile path
echo %ComputerName% # Computer name
echo %UserName% # Current user
IIS Quick Paths
- IIS Manager:
%windir%\system32\inetsrv\InetMgr.exe - Default Website:
%SystemDrive%\inetpub\wwwroot - Default Logs:
%SystemDrive%\inetpub\logs\LogFiles\W3SVC1\ - IIS Config:
%windir%\system32\inetsrv\config\applicationHost.config
Log File Information
- Naming Convention:
ex[YYMMDD].log(example:ex241201.log) - Key Fields: date, time, c-ip, cs-method, cs-uri-stem, sc-status, time-taken
- Status Codes: 200=OK, 404=Not Found, 500=Server Error, 403=Forbidden