PowerShell for System Administrators

Why PowerShell Matters

PowerShell isn't just a Windows shell -- it's a full automation platform that every Windows system administrator should master. With 15+ years in IT, I've seen the transition from batch files and VBScript to PowerShell, and the difference is night and day. PowerShell gives you programmatic access to everything: Active Directory, Hyper-V, file systems, the registry, WMI, and more.

If you're spending more than 5 minutes on a repetitive task, there's a PowerShell way to automate it. Period.

Getting Started with AD PowerShell

The ActiveDirectory module is installed by default on Domain Controllers. For remote management, install the RSAT tools on your workstation:

Install-WindowsFeature RSAT-AD-Tools

Essential AD commands every admin should know:

• Get-ADUser -Filter * -Properties DisplayName,Email,LastLogonDate -- List all users with key properties
• Get-ADUser -Filter {Enabled -eq $false} -Properties LastLogonDate -- Find disabled accounts
• Get-ADUser -Filter {LastLogonDate -lt (Get-Date).AddDays(-90)} -- Find users who haven't logged on in 90 days
• New-ADUser -Name "John Doe" -SamAccountName "jdoe" -Enabled $true -- Create a new user
• Set-ADUser -Identity "jdoe" -Description "Marketing Dept" -- Update user attributes
• Disable-ADAccount -Identity "jdoe" -- Disable an account
• Get-ADGroupMember "Domain Admins" -- List members of a security group
• New-ADOrganizationalUnit -Name "Departments" -ProtectedFromAccidentalDeletion $true -- Create a protected OU

Hyper-V Automation

The Hyper-V PowerShell module lets you manage VMs programmatically. This is invaluable for homelab automation:

• Get-VM -- List all VMs with status, CPU, and memory allocation
• Start-VM -Name "DC01" -- Start a VM
• Stop-VM -Name "DC01" -TurnOff -- Force stop a VM
• CheckPoint-VM -Name "DC01" -SnapshotName "BeforeUpdate" -- Create a checkpoint before maintenance
• New-VM -Name "WebServer" -MemoryStartupBytes 4GB -VhdPath "D:\VMs\WebServer.vhdx" -- Create a new VM
• Set-VMProcessor -VMName "WebServer" -Count 4 -- Assign CPU cores
• Get-VMSwitch -- List virtual switches
• New-VMSwitch -Name "InternalSwitch" -SwitchType Internal -- Create an internal virtual switch

Combine these with scheduled tasks for automated VM maintenance. For example, stop all non-essential VMs at 10 PM and start them at 6 AM:

Get-VM | Where-Object {$_.Name -notlike "DC*" -and $_.Name -notlike "FS*"} | Stop-VM -TurnOff

File System and Disk Management

PowerShell makes file system operations fast and scriptable:

• Get-ChildItem -Path "C:\Logs" -Recurse | Where-Object {$_.LastWriteTime -lt (Get-Date).AddDays(-30)} -- Find files older than 30 days
• Get-ChildItem -Path "D:\Backups" | Sort-Object Length -Descending | Select-Object -First 10 -- List largest backup files
• Get-Volume -- Check disk space across all volumes
• Get-PSDrive -PSProvider FileSystem | Where-Object {$_.Free / 1GB -lt 50} -- Find drives with less than 50GB free
• Compress-Archive -Path "C:\Data\OldFiles" -DestinationPath "D:\Archive\OldFiles.zip" -- Compress old files

System Information and Monitoring

• Get-CimInstance Win32_Processor -- CPU details
• Get-CimInstance Win32_ComputerSystem -- System model, RAM, manufacturer
• Get-CimInstance Win32_OperatingSystem -- OS version, build, boot time
• Get-CimInstance Win32_Service | Where-Object {$_.State -eq "Stopped"} -- Stopped services
• Get-EventLog -LogName System -EntryType Error -Newest 20 -- Recent system errors
• Get-Process | Sort-Object WorkingSet -Descending | Select-Object -First 10 -- Top 10 memory-consuming processes

Useful Automation Scripts

Automated user offboarding:

Disable-ADAccount -Identity $username
Set-ADUser -Identity $username -AccountNotDelegated $true
Add-ADGroupMember -Identity "Password Reset Operators" -Members $username
Move-ADObject -Identity (Get-ADUser $username).DistinguishedName -TargetPath "OU=Disabled,DC=corp,DC=local"

Weekly stale account report:

Get-ADUser -Filter {Enabled -eq $true} -Properties LastLogonDate | Where-Object {$_.LastLogonDate -lt (Get-Date).AddDays(-60)} | Select-Object Name,LastLogonDate,EmailAddress | Export-Csv -Path "C:\Reports\StaleAccounts.csv"

VM health check:

Get-VM | Select-Object Name,State,CPUUsage,MemoryAssigned,Status | Format-Table

PowerShell Best Practices

• Use parameter splatting -- For commands with many parameters, use a hashtable: $params = @{Name="John";SamAccountName="jdoe"}; New-ADUser @params
• Pipeline everything -- PowerShell's strength is piping objects between cmdlets. Get-ADUser | Where-Object | Select-Object | Export-Csv
• Use -WhatIf and -Confirm -- Test destructive commands safely before running them
• Write functions, not just scripts -- Functions can be imported, piped, and reused. Scripts are one-off
• Use try/catch for error handling -- Don't let failed commands break your script. Use try { } catch { Write-Error }
• Comment your code -- Even simple scripts need documentation for the next person (which might be you in 6 months)