Change Linux VM passwords via PowerCLI

pass.ps1

# PowerCLI password script
# By: Jason Greene
# Get vCenter login
$vCenter = Read-Host -Prompt "Enter the vCenter hostname:"

Write-Host "Enter vCenter login credentials"
$cred1 = (Get-Credential)

# Ask for new/old password
$oldpw = Read-Host -Prompt "Enter the OLD root password" -AsSecureString
$newpw = Read-Host -Prompt "Enter the NEW root password" -AsSecureString

# Decrypt for use
$oldpw = [System.Runtime.InteropServices.Marshal]::PtrToStringAuto([System.Runtime.InteropServies.Marshal]::SecureStringToBSTR($oldpw))
$newpw = [System.Runtime.InteropServices.Marshal]::PtrToStringAuto([System.Runtime.InteropServies.Marshal]::SecureStringToBSTR($newpw))

# Connect to vCenter
Connect-VIServer -Server $vCenter -Credential $cred1 -Force > $null

# Get VMs
$vms = Get-VM -Name <vms here> | where {$_.PowerState -eq "PoweredOn"

# Connect to each and change pw
foreach ($vm in $vms){
   Write-Host "Connecting to $vm..."
   Write-Host "Changing root password on $vm..."
   Invoke-VMScript -VM $vm -ScriptText "cat /etc/shadow |grep root" -ScriptType Bash -GuestUser root -GuestPassword $oldpw | Select-Object ScriptOutput
# Sent to > $null becuase the output is an error but the command works. 
   Invoke-VMScript -VM $vm -ScriptText "echo -e '$newpw''\n''$newpw' | passwd" -ScriptType Bash -GuestUser root -GuestPassword $oldpw > $null
   Invoke-VMScript -VM $vm -ScriptText "cat /etc/shadow |grep root" -ScriptType Bash -GuestUser root -GuestPassword $oldpw | Select-Object ScriptOutput
   }
   Disconnect-VIServer -confirm:$false