Active Directory Lightweight Directory Services (AD LDS): The Definitive Guide for Architects & Troubleshooters

Lightweight, secure, and application-centric—Active Directory Lightweight Directory Services (AD LDS), formerly ADAM, is a flexible LDAP directory for app identities and data—without requiring full AD DS membership or domain controllers.

What is AD LDS? (Definition)

Active Directory Lightweight Directory Services (AD LDS) is a Microsoft directory service that exposes a standards-based LDAP endpoint (including LDAPS) for directory-enabled applications—without the need to deploy or depend on an Active Directory Domain Services forest. Each instance carries its own schema, security boundary, and data store, and multiple instances can co-exist on a single server.

Former Name: ADAM (Active Directory Application Mode) in Windows Server 2003/2003 R2, rebranded to AD LDS in Windows Server 2008.
Lightweight by design: No domain controllers, no GPO, no DNS dependency—just the essentials for application identity and attribute storage.
LDAP-based access: Interoperable with any LDAP-aware client SDK or tool (LDP, ldifde, csvde, ADSI, .NET SDS, etc.).
Customizable schema per instance: Extend safely for the app without touching enterprise AD DS schema.
Multi-instance support: Run several isolated instances on the same host with distinct ports and data sets.

Key Points

Ideal for application directories when AD DS is overkill or politically restricted.
Isolated schema = agility and low blast radius for changes.
Supports Windows principals or local AD LDS users for authentication.
Multi-master replication for HA and scale-out.
Secured with SSL/TLS, SASL, and granular ACLs.

Top 10 FAQs — Definition & Basics

Is AD LDS a replacement for AD DS? No—it complements AD DS for app-specific directories.
Does AD LDS require domain controllers? No. It’s independent of domains and GPOs.
Does it support LDAPS? Yes. Use certificates for TLS.
Can I run multiple instances on one server? Yes, each with its own ports and data.
Can apps bind with service accounts? Yes—Windows accounts or AD LDS local users.
Is schema extension risky? Lower risk than AD DS—scoped to the instance.
Is replication multi-master? Yes—supports writeable replicas.
Where is data stored? ESE (Jet) like AD DS, per instance.
Can AD LDS integrate with AD DS? Yes—e.g., for auth via security principals or sync.
Is group policy available? No—AD LDS manages directory data only.

Why AD LDS? (Purpose & When to Use)

AD LDS shines when applications require a secure, standards-based directory without the operational burden or political sensitivity of granting access to the enterprise Active Directory. Typical examples include customer-facing portals, partner directories, isolated identity stores for legacy apps, and multi-tenant deployments where per-tenant schemas differ.

Deployment Scenarios

Customer/partner directory for web apps—no exposure of internal AD DS.
Identity isolation for multi-tenant solutions (one instance per tenant).
Extranet with limited, schema-specific attributes and ACLs.
Dev/Test environments simulating LDAP without touching AD DS.
Legacy apps requiring strict schema and attribute control.

Top 10 FAQs — Purpose & Fit

When should I prefer AD LDS over AD DS? When apps need LDAP but not domain features.
Is AD LDS good for public identities? Yes, with proper ACLs and TLS.
Does AD LDS reduce AD DS attack surface? Yes—apps no longer need broad AD DS access.
Can AD LDS support RBAC? Yes, via ACLs and security groups.
Is it suitable for high-read workloads? Yes, and replicas can scale reads.
Can I stage schema changes? Yes—test in a separate instance safely.
Can AD LDS back an SSO flow? It can back an app’s auth store; SSO depends on the app layer.
Does it support OAuth/OIDC? Not natively; use an identity provider that can query LDAP.
Can it store non-user objects? Yes—any object class defined in the schema.
Is there built-in password policy? Yes—configurable at the instance/app partition level.

Core Architecture: Instances, Partitions, Ports, Security

An AD LDS deployment consists of one or more instances (each with a configuration, schema, and one or more application partitions), exposed via ports you choose at setup (e.g., LDAP: 389 + n, LDAPS: 636 + n). Authentication can use Windows security principals or AD LDS local users. Secure comms rely on TLS (LDAPS); authorization is controlled by ACLs on directory objects/attributes.

Security Building Blocks

TLS certificates (service certs with proper EKUs and subject/SANs).
SASL binds (Kerberos/NTLM) or simple binds with StartTLS/LDAPS.
Fine-grained ACLs, admin roles, and delegation models.
Auditing via Windows event logs and LDAP diagnostics.

Performance & HA

Multi-master replication with conflict resolution.
Read scaling via additional replicas behind load balancers.
Jet/ESE database tuned similarly to AD DS.
Regular online defrag and backup for stability.

Top 10 FAQs — Architecture

Do I need separate servers for replicas? Recommended for HA/perf.
Are ports fixed? No—set at instance creation.
Can I use Windows groups to manage access? Yes, if you enable Windows principal mapping.
Is cross-instance replication supported? Only within a replication set for the same instance.
How do I segregate tenants? Separate instances (and optionally servers).
Is the schema shared across instances? No—schema is per instance.
Can I encrypt data at rest? Use OS volume encryption and secure backups.
Does AD LDS have a Global Catalog? No—GC is an AD DS concept.
Can I audit attribute changes? Yes—enable directory service auditing.
Is backup application-consistent? Use VSS or ntdsutil/Windows Server Backup.

Installing & Configuring AD LDS

Installation can be done via Server Manager, dism, or PowerShell. Below is a reliable, idempotent flow:

PowerShell — Install Feature & Create an Instance

# Install AD LDS feature
Install-WindowsFeature -Name ADLDS -IncludeManagementTools

# Create a new AD LDS instance (interactive wizard alternative)
# Replace values as needed
$instanceName   = "AppDirectory01"
$ldapPort       = 50000
$ldapsPort      = 50001
$instancePath   = "C:\ADLDS\AppDirectory01"
$serviceAccount = "NT AUTHORITY\NetworkService"  # or 'DOMAIN\ServiceAcct'

# Create directories
New-Item -ItemType Directory -Path $instancePath -ErrorAction SilentlyContinue | Out-Null

# Use adaminstall unattended file (INF) for repeatability
$inf = @"
[ADAMInstall]
InstallType=Unique
InstanceName=$instanceName
LocalLDAPPortToListenOn=$ldapPort
LocalSSLPortToListenOn=$ldapsPort
Administrator=BUILTIN\Administrators
DataFilesPath=$instancePath\Data
LogFilesPath=$instancePath\Logs
ServiceAccount=$serviceAccount
ImportLDIFFiles=Yes
# Provide an initial LDF like MS-User.ldf (ships with AD LDS) or your own schema file
LdifFiles=MS-User.ldf
"@
$infPath = Join-Path $env:TEMP "ADLDS-$instanceName.inf"
$inf | Set-Content -Path $infPath -Encoding ASCII

# Silent install
& "$env:SystemRoot\ADAM\adaminstall.exe" /answer:$infPath /quiet

Verify Ports, Service, and Health

# Confirm service
Get-Service -Name "ADAM_$($instanceName)" | Format-List *

# Test LDAP/LDAPS connectivity
Test-NetConnection -ComputerName localhost -Port $ldapPort
Test-NetConnection -ComputerName localhost -Port $ldapsPort

# Verify listeners
netstat -ano | findstr :$ldapPort
netstat -ano | findstr :$ldapsPort

Top 10 FAQs — Setup

Where are sample schema LDFs? In %SystemRoot%\ADAM.
Can I use a custom service account? Yes—use a secure managed account if possible.
Which ports should I pick? Avoid conflicts; document them and open firewalls.
Can I automate with unattended installs? Yes—via INF and adaminstall.exe.
Is LDAPS mandatory? Highly recommended for production.
Can I co-host multiple instances? Yes—ensure unique ports and paths.
How do I seed data? With ldifde/csvde imports or PowerShell/ADSI.
How do I bind initially? Use an admin mapped account or the AD LDS admin user.
How do I enable auditing? Via Local Security Policy → Advanced Audit Policy.
What about backups? Use VSS (Windows Server Backup) and ntdsutil.

Schema Design & Extension (Safely)

Design the schema around application queries and lifecycle. Keep core attributes minimal; add extended attributes only when justified. Prefer reusing standard classes where possible.

Change Control Checklist

Model objects and attributes; map to search filters and indexes.
Version schema with LDF files; store in source control.
Test schema on a staging instance and synthetic datasets.
Automate extension with signed LDFs; rollback plan ready.
Measure query latency before/after; adjust indexes.

PowerShell — Applying a Schema LDF

# Apply a schema extension LDF to AD LDS
$server    = "localhost:50000"
$cred      = Get-Credential  # AD LDS admin or mapped Windows admin
$ldfPath   = "C:\LDIF\custom-schema.ldf"

ldifde -i -f $ldfPath -s $server -k -j C:\LDIF\logs

Top 10 FAQs — Schema

Can I reuse AD DS classes? Yes—many standard classes are available; extend only when needed.
How do I create indexes? Via LDF (attributeSchema with searchFlags).
Can I remove attributes later? Removing is complex; deprecate and stop referencing.
Do schema changes replicate? Yes—across replicas of the same instance.
How to avoid OID collisions? Use an enterprise OID arc for custom classes/attributes.
What’s the safest rollout? Staged: Dev → Test → Pilot → Prod.
How to document schema? Keep LDFs plus markdown specs in version control.
Can I limit who extends schema? Yes—role-based delegation.
How to validate LDF syntax? Test on a disposable instance; check event logs.
How to track schema versions? Maintain a cn=SchemaVersion config object.

Authentication, Authorization & Encryption

AD LDS supports both Windows security principals and local AD LDS users. Authorization uses ACLs on objects/attributes; communications should always be protected with LDAPS (or StartTLS) using a server certificate whose subject/SAN matches the host name that clients use.

PowerShell — Bind & Test Queries

$server   = "lds01.contoso.com:50001"  # LDAPS port
$baseDN   = "CN=AppPartition,DC=contoso,DC=com"
$filter   = "(objectClass=person)"
$cred     = Get-Credential

# Using .NET DirectorySearcher for AD LDS
$root = New-Object System.DirectoryServices.DirectoryEntry("LDAP://$server/$baseDN",$cred.UserName,$cred.GetNetworkCredential().Password,[System.DirectoryServices.AuthenticationTypes]::SecureSocketsLayer)
$searcher = New-Object System.DirectoryServices.DirectorySearcher($root)
$searcher.Filter = $filter
$searcher.PageSize = 500
$searcher.FindAll() | ForEach-Object {
    $_.Properties["cn"]
}

TLS Certificate Sanity Check

# Check that AD LDS is presenting the expected certificate on LDAPS
$server = "lds01.contoso.com"
$port   = 50001
$tcp    = New-Object Net.Sockets.TcpClient($server,$port)
$ssl    = New-Object Net.Security.SslStream($tcp.GetStream(), $false, ({$true}))
$ssl.AuthenticateAsClient($server)
$cert   = New-Object System.Security.Cryptography.X509Certificates.X509Certificate2 $ssl.RemoteCertificate
$cert | Format-List Subject, NotBefore, NotAfter, Thumbprint, EnhancedKeyUsageList

Top 10 FAQs — Security

Can I force LDAPS only? Yes—block plain LDAP at the firewall and configure apps for LDAPS.
Do I need a public CA? Internal CA is fine if all clients trust it.
How do I rotate certs? Install the new cert, update bindings, restart service during window.
Can I use gMSA? For services on domain-joined hosts—applicable if Windows principal mapping is used.
Is password policy configurable? Yes—per application partition.
How to implement least privilege? Grant read/search/write at OU/attribute granularity.
How to audit failed binds? Enable Directory Service Access auditing; monitor Security log.
How to prevent anonymous binds? Disable anonymous access and require auth + TLS.
Does AD LDS support fine-grained password policies? Yes—policy objects in the app partition.
How to secure replication? Use IPsec/TLS, firewall scoping, and dedicated replication networks.

Administration & Day-2 Operations

Admins manage AD LDS using ADSI Edit, LDP, ldifde/csvde, and PowerShell. Below are frequent tasks you can automate.

PowerShell — CRUD Examples (Users, Groups, Binds)

# Create an AD LDS user
$server  = "localhost:50000"
$baseDN  = "OU=People,CN=AppPartition,DC=contoso,DC=com"
$cred    = Get-Credential
$cn      = "john.doe"
$dn      = "CN=$cn,$baseDN"

$entry = New-Object DirectoryServices.DirectoryEntry("LDAP://$server/$baseDN",$cred.UserName,$cred.GetNetworkCredential().Password)
$newUser = $entry.Children.Add("CN=$cn","user")
$newUser.Properties["sn"].Add("Doe") | Out-Null
$newUser.Properties["userPassword"].Add("P@ssw0rd!") | Out-Null
$newUser.CommitChanges()

# Create a group and add a member
$groupDN = "CN=AppReaders,OU=Groups,CN=AppPartition,DC=contoso,DC=com"
$groupParent = New-Object DirectoryServices.DirectoryEntry("LDAP://$server/OU=Groups,CN=AppPartition,DC=contoso,DC=com",$cred.UserName,$cred.GetNetworkCredential().Password)
$group = $groupParent.Children.Add("CN=AppReaders","groupOfNames")
$group.Properties["member"].Add($dn) | Out-Null
$group.CommitChanges()

PowerShell — Bulk Import (CSV → LDIF → AD LDS)

# Convert CSV to LDIF for bulk user creation
$csv = Import-Csv .\users.csv  # columns: cn,sn,givenName,userPassword,ou
$ldif = @()
foreach($r in $csv){
$dn = "CN=$($r.cn),OU=$($r.ou),CN=AppPartition,DC=contoso,DC=com"
$ldif += @"
dn: $dn
changetype: add
objectClass: user
cn: $($r.cn)
sn: $($r.sn)
givenName: $($r.givenName)
userPassword: $($r.userPassword)

"@
}
$ldif -join "`r`n" | Set-Content .\bulk.ldif -Encoding ASCII
ldifde -i -f .\bulk.ldif -s localhost:50000 -k -j .\logs

Backups & Recovery

# VSS backup (Windows Server Backup)
# GUI or PowerShell (WBADMIN). Example (full volume where AD LDS data/logs reside):
wbadmin start backup -backupTarget:E: -include:C: -allCritical -quiet

# AD LDS metadata cleanup if removing a failed replica (use ntdsutil)
ntdsutil "roles" "connections" "connect to server lds01" quit "metadata cleanup" "select operation target" ...

Top 10 FAQs — Operations

How to script user lifecycle? PowerShell with ADSI and LDIF is effective.
How to monitor health? PerfMon counters, event logs, and synthetic binds/queries.
How to rotate service account passwords? Use managed accounts or scheduled rotations.
How to patch safely? Stagger across replicas; validate pre/post health.
How to manage indices? Through schema updates; assess query plans.
Can I delegate OU admins? Yes—ACL the OU subtree and attributes.
How to export data? ldifde -f export.ldf with baseDN + filters.
How to throttle? Use connection limits and query timeouts at the app layer.
How to document? Store INF/LDF/PowerShell in a repo; tag by instance.
How to lint LDIF? Import into a disposable instance; parse errors in logs.

Replication, Performance & Troubleshooting

AD LDS uses multi-master replication. Ensure consistent schema across replicas, stable network routes, and predictable ports. Use health scripts to detect backlog, conflicts, and query slowdowns early.

PowerShell — Replication Snapshot & Conflict Scan

# Basic replication verification via event logs and synthetic queries
$servers = @("lds01:50000","lds02:50000")
$baseDN  = "CN=AppPartition,DC=contoso,DC=com"
$filter  = "(objectClass=*)"
$cred    = Get-Credential

foreach($s in $servers){
  Write-Host "----- $s -----"
  $root = New-Object DirectoryServices.DirectoryEntry("LDAP://$s/$baseDN",$cred.UserName,$cred.GetNetworkCredential().Password)
  $searcher = New-Object DirectoryServices.DirectorySearcher($root)
  $searcher.Filter = $filter
  $searcher.SizeLimit = 1
  ($searcher.FindOne()).Properties["whenchanged"]
  Get-WinEvent -LogName "Directory Service" -ComputerName ($s.Split(":")[0]) -MaxEvents 20 | 
    ?{ $_.Id -in 1084,1088,1388,1389,1390 } | 
    Select TimeCreated, Id, ProviderName, Message
}

Performance — Hot Queries & Indexing

# Quick latency harness for hot queries
$server = "lds01:50000"
$baseDN = "CN=AppPartition,DC=contoso,DC=com"
$cred   = Get-Credential
$filters = @("(uid=j*)","(mail=*@contoso.com)","(&(objectClass=person)(givenName=John))")

foreach($f in $filters){
  $t = Measure-Command {
    $root = New-Object DirectoryServices.DirectoryEntry("LDAP://$server/$baseDN",$cred.UserName,$cred.GetNetworkCredential().Password)
    $s = New-Object DirectoryServices.DirectorySearcher($root)
    $s.Filter = $f; $s.PageSize = 1000; $s.SizeLimit = 1000
    $s.FindAll() | Out-Null
  }
  "{0} -> {1} ms" -f $f,$t.TotalMilliseconds
}

LDAPS & Cipher Hygiene

# Validate protocol versions and ciphers (requires OS tooling)
# Ensure TLS1.2+ is enabled; disable SSLv3/TLS1.0/1.1 at OS level using registry/GPO
# Check certificate EKUs: Server Authentication (1.3.6.1.5.5.7.3.1)

Top 10 FAQs — Troubleshooting

Replication not starting? Check connectivity, time sync, firewall, same schema versions.
Slow queries? Add indexes, reduce attributes returned, restrict search scope.
LDAPS failures? Validate cert chain, SANs, EKUs; test with openssl s_client or script above.
Bind errors? Confirm account status, password policy, and auth type.
Conflicts? Examine event IDs; resolve authoritative values and re-seed.
High CPU on writes? Review transaction logs, defrag, increase IOPS, revisit schema design.
Backlog? Check network latency, bursty writes, and replica health.
Port conflicts? Reconfigure instance ports or move instances.
Access denied? Re-evaluate ACLs on objects/attributes and token mappings.
Backup restore validation? Test on an isolated host; avoid USN rollbacks.

Integration Patterns: AD DS, MIM, Apps & Entra ID

While AD LDS is independent of AD DS, many enterprises integrate the two for sign-in or attribute sync. For cloud-facing apps, you might sync identities into Microsoft Entra ID (formerly Azure AD) via MIM/custom jobs, using AD LDS as the source of truth.

Option A — Use AD LDS Directly from the App

App binds to AD LDS via LDAPS with a service account.
App enforces its own auth flows; AD LDS stores credentials and attributes.
Best when the app must own identities and schema.

Option B — Sync to AD DS or Entra ID

Use MIM/DirSync/custom ETL to publish a subset of objects.
Leverage SSO and modern protocols through Entra ID while maintaining AD LDS as the master.
Great for external users or staged migrations.

Top 10 FAQs — Integration

Can AD LDS be a primary identity store? Yes—many apps use it as their master directory.
How do I sync to Entra ID? Via MIM/custom code reading LDAP, writing to Graph API.
Do I need AAD Connect? Not for AD LDS; AAD Connect targets AD DS. Use MIM or custom.
Can I use SCIM? Not natively; implement a SCIM service backed by AD LDS.
How to map passwords? Use secure bindings; avoid reversible passwords; consider app-owned auth.
How to ensure privacy? Publish only required attributes; encrypt in transit and at rest.
Can I enforce MFA? At the app/IdP layer (e.g., Entra ID), not within AD LDS.
Is there an out-of-box sync? No—tooling like MIM or custom ETL is typical.
How to handle duplicates? Use immutable IDs and authoritative source precedence.
Can I write back from Entra? Possible with custom flows; plan conflict resolution.

Graph API Aids (for Hybrid & App Validation)

Although AD LDS itself isn’t managed via Graph, you can use Microsoft Graph API to validate the cloud side of hybrid patterns (app registrations, service principals, secret expirations, directory objects) when AD LDS syncs identities upstream.

PowerShell (Graph SDK) — App Secrets & Cert Expiry Report

# Requires Microsoft.Graph PowerShell SDK
# Find expiring app secrets/certs that feed apps reading from AD LDS
Connect-MgGraph -Scopes "Application.Read.All","Directory.Read.All"

$threshold = (Get-Date).AddDays(30)
Get-MgApplication -All | ForEach-Object {
  $app = $_
  $secrets = Get-MgApplicationPassword -ApplicationId $app.Id -ErrorAction SilentlyContinue
  $certs   = Get-MgApplicationKeyCredential -ApplicationId $app.Id -ErrorAction SilentlyContinue
  foreach($s in $secrets){ if($s.EndDateTime -lt $threshold){ 
    [pscustomobject]@{ AppDisplayName=$app.DisplayName; Type="Secret"; Expires=$s.EndDateTime } 
  }}
  foreach($c in $certs){ if($c.EndDateTime -lt $threshold){ 
    [pscustomobject]@{ AppDisplayName=$app.DisplayName; Type="Cert"; Expires=$c.EndDateTime } 
  }}
} | Sort-Object Expires | Format-Table -AutoSize

PowerShell (Graph SDK) — Orphaned Service Principals

# Catch orphaned service principals that apps might still call
Connect-MgGraph -Scopes "Application.Read.All","Directory.Read.All"

$apps = Get-MgApplication -All
$spns = Get-MgServicePrincipal -All | Group-Object AppId -AsHashTable -AsString
$apps | Where-Object { -not $spns.ContainsKey($_.AppId) } |
  Select-Object DisplayName, AppId | Format-Table -AutoSize

Top 10 FAQs — Graph & Hybrid

Does Graph manage AD LDS? No—Graph manages Entra ID; use it for hybrid validation.
How to sync AD LDS users to Entra? Custom ETL or MIM, then verify with Graph queries.
Can Graph read LDAP directly? No—Graph reads Entra ID objects only.
Do I need admin consents? Yes—appropriate Graph scopes are required.
How to secure Graph secrets? Use cert-based auth and rotate.
How to correlate IDs? Maintain immutable IDs from AD LDS to Entra.
Can I trigger sync via Graph? Usually no; sync is your job—Graph is the target API.
How to monitor app outages? Alert on secret/cert expiry, failed logins, and 401/403 telemetry.
How to scope least privilege? Grant minimal Graph scopes needed by your job.
Where to store mappings? In a secure DB with versioned schema maps.

Dev & Test: Using AD LDS from .NET

Developers can use System.DirectoryServices or any LDAP library. Here’s a concise .NET example for binds and searches.

// C# example (DirectoryEntry + DirectorySearcher)
var entry = new DirectoryEntry("LDAP://lds01.contoso.com:50001/CN=AppPartition,DC=contoso,DC=com",
                               "CN=admin,CN=Roles,CN=Configuration", "P@ssw0rd!",
                               AuthenticationTypes.SecureSocketsLayer);
var ds = new DirectorySearcher(entry);
ds.Filter = "(&(objectClass=person)(sn=Doe))";
ds.PageSize = 500;
foreach (SearchResult r in ds.FindAll())
{
    Console.WriteLine(r.Properties["cn"][0]);
}

Top 10 FAQs — Developers

Which SDKs work? .NET SDS, LDAP libraries for Java, Python, Go, etc.
Paging supported? Yes—set PageSize for large searches.
Attribute retrieval cost? Ask for only what you need.
Referral chasing? Usually off in isolated instances.
How to test LDAPS locally? Use a dev cert and hosts file mapping.
How to mock? Spin up a disposable AD LDS instance in CI.
How to handle throttling? Backoff + retry; pool connections.
How to trace queries? Enable LDAP diagnostics and instrument your code.
How to store passwords? Prefer app-layer IAM; if stored in AD LDS, hash properly.
How to internationalize? Store in UTF-8; test collation and filters.

Security Hardening Checklist

Enforce LDAPS; disable anonymous/simple binds without TLS.
Harden OS (CIS baselines), enable audit policies, and restrict admin logons.
Use dedicated service accounts with minimal rights; rotate secrets.
Limit network exposure; place behind reverse proxies or firewalls.
Tune indexes and size limits; cap request/connection quotas.
Back up regularly and test restore; document RPO/RTO.
Separate instances per tenant/application.
Keep schema small; deprecate attributes rather than delete.
Enable monitoring dashboards (event IDs, latency, bind failures).
Review and prune stale accounts/objects periodically.

Top 10 FAQs — Hardening

How to enforce LDAPS? Firewall block plain LDAP, configure clients for LDAPS.
Do I need HSMs? Not required; consider for higher assurance.
Password hash policy? Use strong hashing and long secrets; avoid clear-text.
Service isolation? Run instances under least-privileged accounts.
Network segmentation? Yes—restrict to app tiers and replica peers.
Admin workflow? Break-glass account, MFA on jump hosts, audit every change.
Schema change approvals? RFC-style review + staging.
Backdoor prevention? Regularly diff ACLs and admin groups.
Data minimization? Store only necessary PII; purge stale data.
Key rotation cadence? 90 days (secrets) / 12 months (certs) as a starting point.

Field Runbooks — Quick Win Scripts

1) Health Probe (Bind + Search)

$target = "lds01.contoso.com:50001"
$baseDN = "CN=AppPartition,DC=contoso,DC=com"
$cred   = Get-Credential
try {
  $root = New-Object DirectoryServices.DirectoryEntry("LDAP://$target/$baseDN",$cred.UserName,$cred.GetNetworkCredential().Password,[DirectoryServices.AuthenticationTypes]::SecureSocketsLayer)
  $s = New-Object DirectoryServices.DirectorySearcher($root)
  $s.Filter = "(objectClass=top)"; $s.SizeLimit = 1
  $null = $s.FindOne()
  Write-Host "OK: Bind + search succeeded"
} catch { Write-Error $_ }

2) Export Everything (Forensics)

ldifde -m -f C:\temp\full-export.ldf -s lds01:50000 -d "CN=AppPartition,DC=contoso,DC=com" -p Subtree -k -j C:\temp\logs

3) Find Stale Accounts

# Example: lastLogonTimestamp-like attribute if present; otherwise use custom attribute
# Adjust attribute names per your schema.
# This shows the pattern; you'll adapt the attribute applied in your instance.
$cutoff = (Get-Date).AddDays(-90)
# Pseudocode placeholder attribute "lastLoginTime"
# Query via DirectorySearcher and filter where lastLoginTime < cutoff.

4) Replication Event Diff

# Compare replication event patterns across two replicas
$nodes = "lds01","lds02"
$ids = 1084,1088,1388,1389,1390
$events = foreach($n in $nodes){ Get-WinEvent -ComputerName $n -LogName "Directory Service" -MaxEvents 200 |
  Where-Object { $ids -contains $_.Id } | Select-Object TimeCreated, Id, MachineName, Message }
$events | Sort-Object TimeCreated | Format-Table -AutoSize

5) Port Drift Detector

# Validate that configured LDAP/LDAPS ports are still open
$targets = @("lds01:50000","lds01:50001","lds02:50000","lds02:50001")
$targets | ForEach-Object {
  $h,$p = $_.Split(":"); Test-NetConnection -ComputerName $h -Port [int]$p
}

Top 10 FAQs — Runbooks

Where to store scripts? Central repo with signed scripts and PR reviews.
How to schedule health checks? Task Scheduler or your monitoring platform.
How to alert? Emit events/metrics; integrate with SIEM.
How to handle secrets? Use Windows Credential Manager or vaults.
How to parameterize? Use JSON config per environment.
How to roll back schema? Deploy a prior LDF version; restore from backup if needed.
How to handle bulk changes? Dry run → snapshot → apply → verify.
How to test failover? Simulate node loss; ensure app retry logic.
How to cap query cost? Timeouts, attribute whitelists, and scope limits.
How to document incidents? Postmortem templates with timelines and RCAs.

Summary: Why Teams Choose AD LDS

AD LDS gives you a secure, scalable, and agile LDAP directory tailored to application needs—no heavy domain baggage, safer schema extension, and cleaner isolation. With the runbooks and scripts above, you can install, secure, operate, and troubleshoot confidently—whether AD LDS is your system of record or a staging directory feeding modern Entra ID experiences.