Mike Griffin

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Filtering With Powershell and Get-ADComputer

Using Powershell to automate Windows administration tasks is a fairly common thing. I wanted to find out which Active Directory Computer accounts were obsolete or have never been used and then move them into a different Organisational Unit to clean things up a little.

Finding the obsolete accounts was easy enough. I wanted to find any computer that hadn’t logged on to the domain in the last year.

$d = [DateTime]::Today.AddDays(-365)
Get-ADComputer -filter {(enabled -eq "true") -and (lastlogondate -le $d)} -properties cn,lastlogondate

This gave me the name and last logon date.

From here, I used

Move-ADObject -Targetpath 'ou=disabled computers,dc=example,dc=com'

and it moved the computer accounts to the disabled computers OU.

The full command was

$d = [DateTime]::Today.AddDays(-365)
Get-ADComputer -filter {(enabled -eq "true") -and (lastlogondate -le $d)} -properties cn,lastlogondate | Move-ADObject -Targetpath 'ou=disabled computers,dc=example,dc=com'

The problem was that this didn’t take into account any computers that hadn’t logged in at all (i.e. they had a null lastlogondate). The first thing I tried was:

Get-ADComputer -filter {(enabled -eq "true") -and (lastlogondate -eq $null)} -properties cn,lastlogondate

but that spat back an error:

Get-ADComputer : Variable: 'null' found in expression: $null is not defined.  At line:1 char:15

After much searching and trying different things, I found that this worked:

Get-ADComputer -filter {enabled -eq "true"} -properties cn,lastlogondate | where {$_.lastlogondate -eq $null}

Unfortunately this takes all the enabled computer accounts and then filters down through them looking for the ones that have a lastlogondate that equals $null. This means that it’s a lot slower than if we were able to apply the filter directly but for my purposes, it worked and that was all I needed.

It’s inportant to remember to put in the -properties section to bring back the lastlogondate as it isn’t returned by default!