Vfrdtyky

To get FQDN of local computer:

[System.Net.Dns]::GetHostByName($env:computerName)

or

[System.Net.Dns]::GetHostByName($env:computerName).HostName

To get FQDN of Remote computer:

[System.Net.Dns]::GetHostByName('mytestpc1')

or

For better formatted value use:

[System.Net.Dns]::GetHostByName('mytestpc1').HostName

• For remote machines make sure host is reachable.

Local Computer FQDN via dotNet class

[System.Net.Dns]::GetHostEntry([string]$env:computername).HostName

or

[System.Net.Dns]::GetHostEntry([string]"localhost").HostName

Reference:

Dns Methods (System.Net)

note: GetHostByName method is obsolete

Local computer FQDN via WMI query

$myFQDN=(Get-WmiObject win32_computersystem).DNSHostName+"."+(Get-WmiObject win32_computersystem).Domain

Write-Host $myFQDN

Reference:

Win32_ComputerSystem class

[System.Net.Dns]::GetHostByName((hostname)).HostName

$env:computerName returns NetBIOS name of the host, so that both previous examples return
netbioshostname.domainsuffix (not FQDN!)
instead of
dnshostname.domainsuffix (FQDN)

for example, host has
FQDN
aa-w2k12sv-storage.something.com
and NetBIOS name
aa-w2k12sv-stor (an easy case, I usually change NetBIOS name)

the hostname utility returns dnshostname, i.e., the first part of FQDN and code

[System.Net.Dns]::GetHostByName((hostname)).HostName

returns the right FQDN

Comment: never use the same NetBIOS and DNS names of AD domains and hosts. If your or 3rd party application writes to the log: "cannot connect to hostname.domainsuffix", what name it tries to resolve? If you see in the log "cannot connect to netbiosname.domainsuffix", no doubt, a lazy programmer added domain suffix to the NetBIOS name and you are sure, this is a bug, and can open a ticket to force them to fix the issue...

I use the following syntax :

$Domain=[System.Net.Dns]::GetHostByName($VM).Hostname.split('.')

$Domain=$Domain[1]+'.'+$Domain[2]

it does not matter if the $VM is up or down...

"$env:computername.$env:userdnsdomain" 

will work if separated out like this

"$env:computername"+"$env:userdnsdomain"

How about this

$FQDN=[System.Net.Dns]::GetHostByName($VM).Hostname.Split('.')

[int]$i = 1

[int]$x = 0

[string]$Domain = $null

do {

    $x = $i-$FQDN.Count

    $Domain = $Domain+$FQDN[$x]+"."

    $i = $i + 1

} until ( $i -eq $FQDN.Count )

$Domain = $Domain.TrimEnd(".")

Here is a way to determine the FQDN of a server based on the "Name" and "DistinguishedName". Works for multiple domains:

$server = Get-ADComputer serverName -Server domainName -Properties * | select Name, DistinguishedName

$domain = $server.DistinguishedName -split ","

$domain = $domain | ? {$_ -like 'DC=*'}

$domain = $domain -join "."

$domain = $domain -replace "DC="

$FQDN = $server.Name + "." + $domain

I have the following add.. I need to separate out the dns suffix from the hostname.. and I only "know" the servers alias shortname... and want to know what the dns suffix is

#example:

#serveralias:     MyAppServer.us.fred.com

#actualhostname:  server01.us.fred.com 

#I "know":        "MyAppServer" .. I pass this on as an env var called myjumpbox .. this could also be $env:computername





$forname                 = $env:myjumpbox

$fqdn                    = [System.Net.Dns]::GetHostByName($forname).Hostname

$shortname               = $fqdn.split('.')[0]

$domainname              = $fqdn -split $fqdn.split('.')[0]+"."

$dnssuf                  = $domainname[1]  

" name parts are- alias: " + $forname + " actual hostname: " + $shortname + " suffix: " + $dnssuf



#returns



name parts are- alias: MyAppServer actual hostname: server01 suffix: us.fred.com

It can also be retrieved from the registry:

Get-ItemProperty -Path 'HKLM:SYSTEMCurrentControlSetServicesTcpipParameters' 

    | % { $_.'NV HostName', $_.'NV Domain' -join '.' }