Using PowerShell credentials without being prompted for a password

The problem with Get-Credential is that it will always prompt for a password. There is a way around this however but it involves storing the password as a secure string on the filesystem.

The following article explains how this works:

Using PSCredentials without a prompt

In summary, you create a file to store your password (as an encrypted string). The following line will prompt for a password then store it in c:\mysecurestring.txt as an encrypted string. You only need to do this once:

read-host -assecurestring | convertfrom-securestring | out-file C:\mysecurestring.txt

Wherever you see a -Credential argument on a PowerShell command then it means you can pass a PSCredential. So in your case:

$username = "domain01\admin01"
$password = Get-Content 'C:\mysecurestring.txt' | ConvertTo-SecureString
$cred = new-object -typename System.Management.Automation.PSCredential `
         -argumentlist $username, $password

$serverNameOrIp = "192.168.1.1"
Restart-Computer -ComputerName $serverNameOrIp `
                 -Authentication default `
                 -Credential $cred
                 <any other parameters relevant to you>

You may need a different -Authentication switch value because I don't know your environment.

There is another way, but...

DO NOT DO THIS IF YOU DO NOT WANT YOUR PASSWORD IN THE SCRIPT FILE (It isn't a good idea to store passwords in scripts, but some of us just like to know how.)

Ok, that was the warning, here's the code:

$username = "John Doe"
$password = "ABCDEF"
$secstr = New-Object -TypeName System.Security.SecureString
$password.ToCharArray() | ForEach-Object {$secstr.AppendChar($_)}
$cred = new-object -typename System.Management.Automation.PSCredential -argumentlist $username, $secstr

$cred will have the credentials from John Doe with the password "ABCDEF".

Alternative means to get the password ready for use:

$password = convertto-securestring -String "notverysecretpassword" -AsPlainText -Force

Regarding storing credentials, I use two functions(that are normally in a module that is loaded from my profile):

#=====================================================================
# Get-MyCredential
#=====================================================================
function Get-MyCredential
{
param(
$CredPath,
[switch]$Help
)
$HelpText = @"

    Get-MyCredential
    Usage:
    Get-MyCredential -CredPath `$CredPath

    If a credential is stored in $CredPath, it will be used.
    If no credential is found, Export-Credential will start and offer to
    Store a credential at the location specified.

"@
    if($Help -or (!($CredPath))){write-host $Helptext; Break}
    if (!(Test-Path -Path $CredPath -PathType Leaf)) {
        Export-Credential (Get-Credential) $CredPath
    }
    $cred = Import-Clixml $CredPath
    $cred.Password = $cred.Password | ConvertTo-SecureString
    $Credential = New-Object System.Management.Automation.PsCredential($cred.UserName, $cred.Password)
    Return $Credential
}

And this one:

#=====================================================================
# Export-Credential
# Usage: Export-Credential $CredentialObject $FileToSaveTo
#=====================================================================
function Export-Credential($cred, $path) {
      $cred = $cred | Select-Object *
      $cred.password = $cred.Password | ConvertFrom-SecureString
      $cred | Export-Clixml $path
}

You use it like this:

$Credentials = Get-MyCredential (join-path ($PsScriptRoot) Syncred.xml)

If the credential file doesnt exist, you will be prompted the first time, at that point it will store the credentials in an encrypted string inside an XML file. The second time you run that line, the xmlfile is there and will be opened automatically.