Category Archives: Windows Server 2019

Windows | 3 Methods to “Unauthorised” DHCP server

There’s a couple of ways to “unauthorised” a DHCP server in Active Directory. Sometimes AD can get in a twist and says “the DHCP can’t be authorised” as it’s already been authorised. This could be potentially related to replication time but the steps below will help you check.

Via the DHCP MMC GUI -> Right click -> “Manage Authorised Servers”

Via CLI

Show authorised list (basically what you see in the GUI)

Netsh DHCP show server

Remove entry: (Netsh DHCP delete server ServerFQDN ServerIP address)

Netsh DHCP delete server 2003-dc1.contoso.com 10.1.192.92

Via ASDIedit MMC

Adding DNS Alias | Replacing File Server

When replacing a file server with new server and new name you probably want to keep the old name and add a redirect. Originally, I thought this was a simple “change the DNS IP” and job done but there’s a little bit more to it than just that!

1) Locate OLDSERVER entry in DNS and delete it.

2) If the OLDSERVER server AD object still exists, you need to delete it. Failing to remove the old computer object will result in this error:

Unable to add NEWSERVER.
as an alternate name for the computer.
The error is: Cannot create a file when that file already exists.
The command failed to complete successfully.

3) Run this command to add the server alias:

netdom computername NEWSERVER /add:OLDSERVER

Note: if you have subdomains in use (sub.domain.com) then you need to specifically define this overwise the object will add “oldserver.domain.com” rather than “oldserver.sub.domain.com”

4) Register the machine in DNS

IPConfig /RegisterDNS

5) Run this command to check the aliases are shown on the machine

netdom computername NEWSERVER /enum

6) Final check to show what SPF entries have been created:

setspn -l NEWSERVER

Ref: https://support.microsoft.com/en-gb/help/3181029/smb-file-server-share-access-is-unsuccessful-through-dns-cname-alias

Netdom: https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2008-R2-and-2008/cc835082(v=ws.10)

Original Post: https://blogs.technet.microsoft.com/askpfeplat/2017/06/19/using-computer-name-aliases-in-place-of-dns-cname-records/

Windows | DHCP PowerShell Options (Cheatsheet)

Managing DHCP on DHCP server:

Add-WindowsFeature -Name DHCP –IncludeManagementTools

Managing DHCP on remote host:

Add-WindowsFeature RSAT-DHCP

Powershell DHCP Module:

Import-Module DhcpServer

Get all DHCP servers in AD

Get-DhcpServerInDC

Get DHCP scope configuration

Get-DhcpServerv4Scope –ComputerName <DHCPServerName>

Get DHCP reservations on scope:

Get-DhcpServerv4Reservation -ComputerName <DHCPServerName> -ScopeId <ScopeID>

Import/Export DHCP Scopes

netsh dhcp server export C:\temp\DHCP.txt all
netsh dhcp server import C:\temp\DHCP.txt all

Note: The temp folder needs to be created

Check DHCP Replication Failover Status

Get-DhcpServerv4Failover -ComputerName <DHCPServerName>

Reference:
https://technet.microsoft.com/en-us/library/jj590708(v=wps.630).aspx

Windows | Remote Management “Could not start Virtual Disk Service (VDS)”

To avoid this error when you remotely managing another servers virtual disks (From “Server Management” you need to follow some steps

Disk Management could not start Virtual Disk Service (VDS) on SERVER-NAME. This can happen if the remote computer does not support VDS, or if a connection cannot be established because it was blocked by Windows Firewall.

For additional information about diagnosing and correcting this problem, see Troubleshooting Disk Management in Disk Management Help.

Step1: 

Check Virtual Disk Service is started on BOTH the local and remote system

Powershell:

Start-Service -Name "vds"

CMD:

net start vds

Step2: 

Add firewall exceptions on BOTH the local and remote system. VOILA! WORKING WITHOUT ANY ERRORS 🙂

netsh advfirewall firewall set rule group="Remote Volume Management" new enable=yes

Step3: 

Use “Server Manager” to connect remotely and access the disk management properties on the remote machine.

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Windows | System “Recovery Partition” After Upgrade

After a Windows 10 or Windows Server (2016/2019) upgrade a new system “recovery partition” gets created at the tailend of the C:\ this isn’t usually a problem for physical machines but for VM it can cause some issues if you wish to “extend” the VDMK/Partition size.

You can quickly remove the partition using “diskpart” and continue your extend. From what I’ve seen this shouldn’t cause any major issues. To be honest we rarely use any of the Windows features for restores as snapshot and backup usually fix them.

diskpart
list disk 
select disk X
list partition 
select partition X
delete partition override

Before:

After:

Windows Time Commands | Cheatsheet

Check time service is running (Local & Remote):

sc query w32time
sc \\HOSTNAME query w32time

Displays all local time information (Local & Remote):

w32tm /query /configuration
w32tm /query /configuration /computer:HOSTNAME

Display Windows Time service status (Local & Remote):

w32tm /query /status
w32tm /query /status /computer:HOSTNAME

Display Windows Time service source (Will return one line: local CMOS vs Server) (Local & Remote):

w32tm /query /source
w32tm /query /source /computer:HOSTNAME

Display a list of peers and their status:

w32tm /query /peers

Displays current time (local source)

Time /T

Resync local computer time against time server: (run on all servers, except time server)

w32tm /resync /rediscover 

Force local computer time to update against domain server (Local & Remote):

w32tm /config /syncfromflags:domhier /update
w32tm /resync /rediscover w32tm /resync
w32tm /config /syncfromflags:domhier /update /computer:HOSTNAME
w32tm /resync /rediscover w32tm /resync

Start time server via CLI (Local & Remote)

net start w32time
SC \\HOSTNAME net start w32time

Restore Windows Time Service (if it has been broken)

net stop W32Time
w32tm /unregister
w32tm /register
net start W32Time
sc query W32Time

Set Time Update NTP source

@echo off
net stop w32time
w32tm /config /syncfromflags:manual /manualpeerlist: 0.uk.pool.ntp.org
w32tm /config /reliable:yes
net start w32time
w32tm /query /peers
PAUSE

Event Viewer Error Message:

Event Type: Error 

Event Source: W32Time 

Event Category: None 
Event ID: 12

Description: Time Provider NtpClient: This machine is configured to use the domain hierarchy to determine its time source, but it is the PDC emulator for the domain at the root of the forest, so there is no machine above it in the domain hierarchy to use as a time source. It is recommended that you either configure a reliable time service in the root domain, or manually configure the PDC to synchronize with an external time source. Otherwise, this machine will function as the authoritative time source in the domain hierarchy. If an external time source is not configured or used for this computer, you may choose to disable the NtpClient.

To resolve the eventID 12:

  • w32tm /register

Reference: