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PowerShell-Interview & Answer
PowerShell-Interview
PowerShell-Interview : Document Resources, Topics, Questions and Tips for a PowerShell Development Interview
Many of the topics/questions may not come directly in your interview, but it would be a good idea to understand them, in order to understand PowerShell better. Which will give you an edge in the interview and leave a better impression if you explain it in details.
Questions & Answer
What is PowerShell?
- PowerShell is a shell designed especially for system administrators.
- Open Source and Platform Independent (Windows/Linux/Mac)
- Object oriented, not text-based
- Built on .NET framework
- Interactive prompt and a scripting environment.
How does powershell differ from other scripting languages
TBD
PowerShell versions and differences
TBD
Execution Policies
Types of Execution Policy?
There are 6 types of execution policies
This is the default. PowerShell will not run any script, including PowerShell profiles.
2. RemoteSigned
PowerShell will run any script that you create locally. But any script that has been detected as coming from the Internet, such as via Internet Explorer, Microsoft Outlook, Mozilla Firefox or Google Chrome must be digitally signed with a code signing certificate that is trusted by the computer.
PowerShell will not run any script unless it has been digitally signed with a trusted code signing certificate.
PowerShell will make no attempts to hinder script execution and will run any script. If the script comes from an untrusted source, like the Internet, you will be prompted once to execute it. Though it is not preferred.
There is also a Bypass policy, which I don’t recommend for daily use. This policy will run any script without question or prompting. The assumption is that you have taken steps outside of Nothing is blocked and there are no warnings or prompts.PowerShell to verify the safety and integrity of the script.
There is no execution policy set in the current scope. If the execution policy in all scopes is Undefined, the effective execution policy is Restricted, which is the default execution policy.
What is the order in which execution policy is evaluated ?
Windows PowerShell determines the effective policy by evaluating the execution policies in the following precedence order –
- Group Policy: Computer Configuration
- Group Policy: User Configuration
- Execution Policy: Process (or PowerShell.exe -ExecutionPolicy) – CURRENT SCOPE
- Execution Policy: CurrentUser – SAVED in HKCU registry
- Execution Policy: LocalMachine – SAVED in HKLM registry
CIM vs WMI
| Stands for Windows Management Instrumentation | Stands for Windows Management Instrumentation | Stand for Common Information Model |
| Old WMI is Microsoft’s initial implementation of CIM | New WMI was released with WMF v3 in 2012 which was compliant to new CIM standards | Vendor-neutral, industry standard way of representing management information |
| Developed by MicroSoft | Developed by MicroSoft | Developed by the DMTF |
| Since PowerShell v1 | Introduced in PowerShell v3 | |
| Microsoft used DCOM (Distributed COM) / RPCs (Remote Procedure Calls) | Uses WSMan and no more DCOM errors | Uses WSMan, a standard developed by DMTF |
| Windows only | Windows only | Any platform |
| Get-WMIObject | Get-CimInstance, Get-CimClass, Invoke-CimMethod | No cmdlets |
| More or less deprecated and you’re connected to LIVE objects and can play with them | Not connected to LIVE objects, stateless relationship with the remote machine | |
| RPC port- 135 | WSMan Port – 5985 (HTTP), 5986(HTTPS) | WSMan Port – 5985 (HTTP), 5986(HTTPS) |
- Uses DCOM/RPC. Uses old-style native code providers and a repository.
- Available only on Windows.
- More or less deprecated, meaning it’s not a focus area for further improvement or development. You’re connected to “live” objects and can play with them.
- Uses WS-MAN (via WinRM service). Supports old-style native code providers and a repository, as well as new-style MI providers.
- Available only on Windows.
- The way forward. If something can talk to “NEW WMI” it should be able to talk to OMI, also. You’re not connected to “live” objects, and have an essentially stateless relationship with the remote machine.
- Uses WS-MAN (OMI code includes the protocol stack). Supports only new-style MI providers.
- Available on any implementing platform. Also the way forward. If something can talk to OMI, it should be able to talk to “NEW WMI” also.
- Defines the standard. Created by DMTF.
- Early versions were implemented as “OLD WMI” by Microsoft, newest version implemented both in “NEW WMI” and OMI by Microsoft and others.
Area of confusion
In 2012 with Windows Management Framework 3, Microsoft releases a new version of WMI. They fail to give it a unique name, which causes a lot of confusion, but it complies with all the latest CIM specifications.
The PowerShell cmdlets that uses this new WMI has CIM in their noun part of the cmdlet, like Get-CimInstance, Get-CimClass, Invoke-CimMethod But these aren’t CIM because CIM isn’t a protocol. They’re talking WS-MAN, which is what the new CIM standard specifies.
Credits:
- https://powershell.org/2015/04/24/management-information-the-omicimwmimidmtf-dictionary/#.W3BpB-gzaUk
- https://richardspowershellblog.wordpress.com/2013/03/24/wmi-vs-cim/
WinRM and WSMan and DCOM
WSMan
- WS-Management or Web Services-Management is a DMTF (Distributed Management task force)
- It is an open standard defining a SOAP-based (Simple Object Access Protocol) protocol for the management of servers, devices, applications and various Web services.
- Vendor Neutral, common way for systems to access and exchange management information across the IT infrastructure.
- Microsoft has implemented the WS-Management standard in Windows Remote Management (WinRM).
- WinRM is a feature of Windows Vista that allows administrators to remotely run management scripts.
- It handles remote connections by means of the WS-Management Protocol, which is based on SOAP (Simple Object Access Protocol).
- DCOM stands for Distributed COM (Component Object Model)
- Used to connect LIVE objects on the remote machine.
- That meant you could get a WMI instance, execute methods, change properties.
- The RPC protocol was designed for that kind of continuous back-and-forth.
- But it is network/memory inefficient due to LIVE objects
Automatic variables
- Describes variables that store state information for PowerShell.
- These variables are created and maintained by PowerShell.
Some very common Automatic Variables
$$ – Contains the last token in the last line received by the session.
$? – Contains the execution status of the last operation. It contains TRUE if the last operation succeeded and FALSE if it failed.
$^ – Contains the first token in the last line received by the session.
$_ – Same as $PSItem. Contains the current object in the pipeline object. You can use this variable in commands that perform an action on every object or on selected objects in a pipeline.
$Args – Contains an array of the undeclared parameters and/or parameter values that are passed to a function, script, or script block. When you create a function, you can declare the parameters by using the param keyword or by adding a comma-separated list of parameters in parentheses after the function name.
$Error – Contains an array of error objects that represent the most recent errors. The most recent error is the first error object in the array ($Error[0]).
$ForEach – Contains the enumerator (not the resulting values) of a ForEach loop. You can use the properties and methods of enumerators on the value of the $ForEach variable. This variable exists only while the ForEach loop is running; it is deleted after the loop is completed. For detailed information
$Home – Contains the full path of the user’s home directory. This variable is the equivalent of the %homedrive%%homepath% environment variables, typically C:\Users<UserName>.
$OFS – $OFS is a special variable that stores a string that you want to use as an output field separator . Use this variable when you are converting an array to a string. By default, the value of $OFS is ” “, but you can change the value of $OFS in your session, by typing $OFS=””. If you are expecting the default value of ” ” in your script, module, or configuration output, be careful that the $OFS default value has not been changed elsewhere in your code.
$PID – Contains the process identifier (PID) of the process that is hosting the current Windows PowerShell session.
$Profile – Contains the full path of the Windows PowerShell profile for the current user and the current host application. You can use this variable to represent the profile in commands. For example, you can use it in a command to determine whether a profile has been created
Know more:
Get-Help about_Automatic_Variables
Use a hash table to splat parameter name and value pairs. You can use this format for all parameter types, including positional and named parameters and switch parameters.
$HashArguments = @{
Path = "test.txt"
Destination = "test2.txt"
WhatIf = $true
}
Copy-Item @HashArguments
For using Local variables in remote sessions
$ps = "Windows PowerShell"
Invoke-Command -ComputerName S1 -ScriptBlock {
Get-WinEvent -LogName $Using:ps
}
How to map network drives using PowerShell and it should persist
Using WScript.Network COM object
$Net = $(New-Object -ComObject Wscript.Network ) $Net.MapNetworkDrive( "S:", '\\localhost\filemov',$true )
Using net command from Native CMD
net use M: \\Server\Share /Persistent:Yes
Using PSDrive
New-PSDrive -Persist -Name “y” -PSProvider “FileSystem” -Root “\\localhost\filemov”
How to form credentials objects in PowerShell
$UserName = 'Prateek' $Password = 'Password@123' | ConvertTo-SecureString -AsPlainText -Force # method 1 [pscredential]::new($Username,$Password) # method 2 New-Object System.Management.Automation.PSCredential($UserName,$Password)
How to find installed applications on a windows machine
Get-ItemProperty HKLM:\Software\Microsoft\Windows\CurrentVersion\Uninstall\* | Select-Object DisplayName, DisplayVersion, Publisher, InstallDate
How to identify if a windows machine is 32/64 bit
# method 1 $env:PROCESSOR_ARCHITECTURE # method 2 [Environment]::Is64BitOperatingSystem # method 3 gwmi win32_operatingsystem | select osarchitecture # method 4 (wmic os get osarchitecture)[2]
How to find operating system name/version
(Get-WmiObject Win32_OperatingSystem).Name (Get-WmiObject Win32_OperatingSystem).caption
What is String Interpolation in PowerShell
#Require statement
- The #Requires statement prevents a script from running unless specific conditions the PowerShell version, modules, snap-ins, module and snap-in version, and edition prerequisites are met.
- If the prerequisites are not met, PowerShell does not run the script.
#Requires -Version <N>[.<n>]
#Requires -PSSnapin <PSSnapin-Name> [-Version <N>[.<n>]]
#Requires -Modules { <Module-Name> | <Hashtable> }
#Requires -PSEdition <PSEdition-Name>
#Requires -ShellId <ShellId>
Parameter binding
By Value
Get-Service bits | Stop-Service
Data-Type/ TypeName of the object decides if it will bind to a function or cmdlet, If you look closely in the help file of the cmdlet, the InputObject accepts ServiceController[] objects from pipeline – Accept pipeline input? True (ByValue)
PS C:\> Get-Help Stop-Service -Parameter inputobject
-InputObject <ServiceController[]>
Specifies ServiceController objects that represent the services to stop. Enter a variable that contains the objects, or type a command or expression that gets the objects.
Required? true
Position? 0
Default value None
Accept pipeline input? True (ByValue)
Accept wildcard characters? false
By PropertyName
$obj = [PSCustomObject]@{
Name = 'icmp'
Value = 'ping'
}
$obj | New-Alias -verbose
Binds parameter on basis of names of the property of the objects coming form the pipeline, you can check these properties like in the following example
PS C:\> Get-Help New-Alias -Parameter Name
-Name <String>
Specifies the new alias. You can use any alphanumeric characters in an alias, but the first character cannot be a number.
Required? true
Position? 0
Default value None
Accept pipeline input? True (ByPropertyName)
Accept wildcard characters? false
PS C:\> Get-Help New-Alias -Parameter Value
-Value <String>
Specifies the name of the cmdlet or command element that is being aliased.
Required? true
Position? 1
Default value None
Accept pipeline input? True (ByPropertyName)
Accept wildcard characters? false
- ByValue with same Type (No Coercion)
- ByPropertyName with same Type (No Coercion)
- ByValue with type conversion (Coercion)
- ByPropertyName with type conversion (Coercion)
Powershell Pipelines
- A pipeline is a series of commands connected by pipeline operators (|) or ASCII 124.
- Each pipeline operator sends the results of the preceding command to the next command.
- A very powerful command chain or “pipeline” that is comprised of a series of simple commands.
- Objects from previous cmdlet binds parameters (ByValue/ByPropertyName) to the cmdlet following the pipeline
- Pipeline processes one object at a time
- Investing Pipeline errors, is mostly investigating what went wrong with the
Parameter Binding
Trace-Command -name ParameterBinding -expression {
Get-Service BITS | Stop-Service
} -pshost
Credits:
- https://www.red-gate.com/simple-talk/sysadmin/powershell/ins-and-outs-of-the-powershell-pipeline/
- https://www.red-gate.com/simple-talk/dotnet/.net-tools/down-the-rabbit-hole–a-study-in-powershell-pipelines,-functions,-and-parameters/
Powershell Scopes
- Global, Local, Script, Private
- The scope that is in effect when PowerShell starts. and is the Default scope
- Variables and functions that are present when PowerShell starts have been created in the global scope. This includes automatic variables and preference variables.
- This also includes variables, aliases, and functions that are in your PowerShell profile.
- The current scope. The local scope can be the global scope or any other scope.
- The scope that is created while a script file runs. Only the commands in the script run in the script scope. To the commands in a script, the script scope is the local scope.
- Items in private scope cannot be seen outside of the current scope. You can use private scope to create a private version of an item with the same name in another scope.
Credits:
Powershell Workflows
- Persist
- Parallelism
- Parallel
- Foreach -Parallel
- Sequence
- InlineScript
How to extend a disk partition using PowerShell
$part = Get-Partition |? {$_.isboot}
$size = Get-PartitionSupportedSize -DriveLetter $part.DriveLetter
Resize-Partition -DriveLetter $part.DriveLetter -Size $size.SizeMax -Verbose
How to write PowerShell scripts that can withstand reboots or Interruptions?
- WorkFlows
- RunOnce Registry key
How to find free space on a drive using PowerShell
PS C:\> Get-PSDrive
Name Used (GB) Free (GB) Provider Root
---- --------- --------- -------- ----
Alias Alias
C 294.11 623.80 FileSystem C:\
Cert Certificate \
D FileSystem D:\
Env Environment
Function Function
HKCU Registry HKEY_CURRENT_USER
HKLM Registry HKEY_LOCAL_MACHINE
Variable Variable
WSMan WSMan
PS C:\> gwmi win32_logicaldisk
DeviceID : C:
DriveType : 3
ProviderName :
FreeSpace : 669797478400
Size : 985600299008
VolumeName : OS
DeviceID : D:
DriveType : 5
ProviderName :
FreeSpace :
Size :
VolumeName :
PS C:\> Get-CimInstance cim_logicaldisk
DeviceID DriveType ProviderName VolumeName Size FreeSpace
-------- --------- ------------ ---------- ---- ---------
C: 3 OS 985600299008 669796954112
D: 5
PS C:\> Get-Volume
DriveLetter FriendlyName FileSystemType DriveType HealthStatus OperationalStatus SizeRemaining Size
----------- ------------ -------------- --------- ------------ ----------------- ------------- ----
C OS NTFS Fixed Healthy OK 623.8 GB 917.91 GB
Image NTFS Fixed Healthy OK 554.41 MB 11.07 GB
NTFS Fixed Healthy OK 334.54 MB 865 MB
DELLSUPPORT NTFS Fixed Healthy OK 539.16 MB 1.07 GB
ESP FAT32 Fixed Healthy OK 433.32 MB 496 MB
D Unknown CD-ROM Healthy Unknown 0 B 0 B
PowerShell does not have support for creating types directly, but instead favors monkey patching using PowerShell’s Adaptive Type System (ATS) to add variables, properties, methods, and ScriptBlocks to a PSObject instance.
- Add-Member
- With ATS you are in control of your own destiny. (If you don’t like the world – change it yourself. [then share to help others]) ~JSnover
Creating methods of an object
TBD
What has been most challenging work you have done.
TBD
Out-Host, Write-Output, Write-Host
TBD
Number of ways to create an object
# 1. Using Hashtables
[pscustomobject]@{
firstname = 'Prateek'
lastname = 'Singh'
}
# 2. Using Select-Object
Select-Object @{n='firstname';e={'Prateek'}},@{n='lastname';e={'Singh'}} -InputObject ''
# 3. Using New-Object and Add-memeber
$obj = New-Object -TypeName psobject
$obj | Add-Member -MemberType NoteProperty -Name firstname -Value 'Prateek'
$obj | Add-Member -MemberType NoteProperty -Name lastname -Value 'Singh'
# 4. Using New-Object and hashtables
$properties = @{
firstname = 'Prateek'
lastname = 'Singh'
}
$o = New-Object psobject -Property $properties; $o
How to rename a variable
PS C:\> $a = 1..3 PS C:\> $a 1 2 3 PS C:\> Rename-Item -Path variable:a -NewName b PS C:\> $b 1 2 3
How to find the largest file in a folder
PS C:\> Get-ChildItem C:\Data\Powershell\PoshBot\ -recurse | Sort-Object Length -desc | Select-Object -f 1
Directory: C:\Data\Powershell\PoshBot\PoshBot\en-US
Mode LastWriteTime Length Name
---- ------------- ------ ----
-a---- 4/19/2018 12:37 AM 97648 PoshBot-help.xml
TBD
| Modules | Snap-ins |
|---|---|
| A package that contains Windows PowerShell commands in form of functions, cmdlets etc. | Are compiled cmdlets in to a DLL written in a .Net language |
| Can be imported directly | Requires Installation, with Admin privileges |
| Extension: .psm1 | Extension: .dll |
| New | Deprecated |
| Get-Module -ListAvailable | Get-PSSnapin -Registered |
| Stored in $env:PSModulePath | Stored in registry: hklm:\SOFTWARE\Microsoft\PowerShell\1\PowerShellSnapIns\ |
Import-Module [name] | Add-PSSnapIn [name] adds the PSSnapIn to the PowerShell Session |
What is a Filter?
A filter is a function that just has a process scriptblock
PS C:\> filter myFilter {
$_
}
PS C:\> @(1,2,3) | myFilter
1
2
3
Other ways to use filters
function myFunction {
$Input
}
Function myFunction {
Process { $_ }
}
How to reverse order of a String
# Method 1
$a='String'.tochararray(); [array]::Reverse($a)
# Method 2
$a = '';for($i=$($Str.Length-1);$i -ge 0;$i--){$a+=$Str[$i]} ; $a
# Method 3
$str[$($str.Length-1)..0] -join ''
How to save credentials in your PowerShell Scripts
- The use ConvertTo-SecureString and ConvertFrom-SecureString without a Key or SecureKey, Powershell will use Windows Data Protection API (DPAPI) to encrypt/decrypt your strings.
- This means that it will only work for the same user on the same computer.
- Using a Key/SecureKey, the AES encryption algorithm is used that allows you to use the stored credential from any machine with any user so long as you know the AES Key that was used.
$user = "UserName" $password = 'Password@123'| ConvertTo-SecureString -AsPlainText -Force | ConvertFrom-SecureString $Creds = New-Object -TypeName System.Management.Automation.PSCredential -ArgumentList $User, ($password | ConvertTo-SecureString)
How to take Passwords input from users in a secure way?
Read-Host -AsSecureString
What is cryptographic algorithm used in Convert To-SecureString ?
- AES – Advanced Encryption Standard
- DPAPI – WIndows Data Protection API is used to encrypt your strings
Credits:
- https://powershell.org/2014/02/01/revisited-powershell-and-encryption
- https://powershell.org/2013/11/24/saving-passwords-and-preventing-other-processes-from-decrypting-them/#.W3FsA-gzaUk
Explain what is the function of $input variable?
- Contains an enumerator that enumerates all input that is passed to a function.
- The $input variable is available only to functions and script blocks (which are unnamed functions).
- In the Process block of a function, the $input variable enumerates the object that is currently in the pipeline.
- When the Process block completes, there are no objects left in the pipeline, so the $input variable enumerates an empty collection.
- If the function does not have a Process block, then in the End block, the $input variable enumerates the collection of all input to the function.
What is $_ and $PSItem variable
Both represents the Current object in pipeline
What are two ways of extending PowerShell?
PSSnapins
Modules
You have a script which uses Read-Host to prompt the user for an IP address. You need to make sure the user inputs a valid IP address. How would you do that ?
- Splitting the address in 4 elements and try to cast them to a [byte]
- A regular expression [regex]
- Cast the input string to the [System.Net.IPAddress] class
- Advanced functions uses CmdletBinding attribute to identify them as functions that act similar to cmdlets.
- Using the
[CmdletBinding()]at the top includes the common parameters to the function :Verbose, Debug, ErrorAction, ErrorVariable, WarningAction, WarningVariable, OutBuffer, PipelineVariable, and OutVariable - WhatIf and Confirm functionalities can be added by using the SupportsShouldProcess in the cmdlet binding attribute
[CmdletBinding(SupportsShouldProcess = $true)] - See
Get-Help about_Functions_CmdletBindingAttribute - Advance functions have following script blocks:
Begin{} Process{} End{} - If script blocks are not defined, anything in body of Advance function is a
Process block
function foo {
[cmdletbinding()]
Param (
[parameter(ValueFromPipeline=$True)]
[string]$Name)
Begin {}
Process{
write-verbose $Name
}
End{}
}
Credits:
- https://ss64.com/ps/syntax-function-input.html
- https://docs.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_functions_advanced?view=powershell-6
| Stream | Number | Contents | Usage | Comments |
|---|---|---|---|---|
| Output/Success/Pipeline | 1 | Output from commands | Write-Output “Write-Output message” | Default stream, all o/p goes to this stream even the end of pipeline |
| Error | 2 | Error messages | Write-Verbose “Write-Verbose message” | |
| Warning | 3 | Warning messages | Write-Warning “Write-Warning message” | |
| Verbose | 4 | Verbose output | Write-Debug “Write-Debug message” | |
| Debug | 5 | Debug messages | Write-Error “Write-Error message” | |
| Information | 6 | General information | Write-Information “Write-Information” | Since PowerShell v5 |
1-6 : Choice of PowerShell Streams
> : Redirection operator
>> : Redirect and append
& : Adding PowerShell Streams
* : All Streams
Examples –
3>&1 - Sends warnings (3) and Success output (1) stream
4>&1 - Sends verbose output (4) and success output (1)
*>&1 - Sends all output streams to Output Stream (1)
Credits:
| Cmdlet | Functionality |
|---|---|
| Out-Host | is the default when you don’t specify anything else |
| Out-Default | In reality, the Out-Host portion of that is unnecessary, because Windows PowerShell has the Out-Default cmdlet hardcoded into the end of the pipeline. That cmdlet simply forwards things to Out-Host |
| Out-Printer | sends output to a printer. |
| Out-File | sends output to a file |
| Out-Grid | Displays your objects in a graphical table with click-to-sort column headers and a search/filter box to help locate specific results |
| Write-Output | Sends output to the pipeline |
CredSSP issues in PowerShell and workarounds
PowerShell remoting to connect to Server-1 which then attempts to connect from Server-1 to Server-2 but the second connection fails, this is a Double Hop issue.
Because, PSRemoting authenticates via Network Logon which works by showing possession of the credential, but since remote server doesn’t have the credential, it fails! the second Hop Server-1 to Server-2.
- PowerShell provides the CredSSP option which performs “Network Clear-text Logon” instead of a “Network Logon”.
- CredSSP Network Clear-text Logon sends clear-text password to the remote Server-1 in clear-text, which eventually is used to authenticate to Server-2, in the second hop.
# On client machine, from where you do the PowerShell Remoting Enable-WSManCredSSP –Role Client –DelegateComputer Server2.ridicurious.com -Force # Checking Get-WSManCredSSP # On Server Enable-WSManCredSSP –Role Server -Force # Usage - Make sure to use CredSSP Authentication Enter-PSSession –ComputerName Server2.ridicurious.com –Credential RidiCurious\administrator –Authentication CredSSP
- This is not constrained delegation. CredSSP passes the user’s full credentials to the server without any constraint.
- And if the Server is compromised, attackers can even read your credentials in plain-text using tools like Mimikatz
What is CredSSP
- The Credential Security Support Provider protocol (CredSSP) is a Security Support Provider that is implemented by using the Security Support Provider Interface (SSPI)
- CredSSP lets an application delegate the user’s credentials from the client to the target server for remote authentication.
- CredSSP provides an encrypted Transport Layer Security Protocol channel (TLS). The client is authenticated over the encrypted channel by using the Simple and Protected Negotiate (SPNEGO) protocol with either Microsoft Kerberos or Microsoft NTLM.
Credits
- https://docs.microsoft.com/en-us/windows/desktop/secauthn/credential-security-support-provider
- https://www.powershellmagazine.com/2014/03/06/accidental-sabotage-beware-of-credssp/
PowerShell Remoting ( PSRemoting )
How to enable PSRemoting on a server?
Server Side
Enable-PSRemoting -Force
# The asterisk is a wildcard symbol for all PCs. If instead you want to restrict computers that can connect, you can replace the asterisk with a comma-separated list of IP addresses or computer names for approved PCs.
Set-Item wsman:\localhost\client\trustedhosts *
# After running that command, you’ll need to restart the WinRM service so your new settings take effect. Type the following cmdlet and then hit Enter:
Restart-Service WinRM
Set-Item wsman:\localhost\client\trustedhosts *
Test-WSMan
or, you can run Get-PSSessionConfiguration cmdlet to see the PowerShell configurations
PS C:\> Get-PSSessionConfiguration
Name : microsoft.powershell
PSVersion : 5.1
StartupScript :
RunAsUser :
Permission : NT AUTHORITY\INTERACTIVE AccessAllowed, BUILTIN\Administrators AccessAllowed, BUILTIN\Remote Management Users
AccessAllowed
Name : microsoft.powershell.workflow
PSVersion : 5.1
StartupScript :
RunAsUser :
Permission : BUILTIN\Administrators AccessAllowed, BUILTIN\Remote Management Users AccessAllowed
Name : microsoft.powershell32
PSVersion : 5.1
StartupScript :
RunAsUser :
Permission : NT AUTHORITY\INTERACTIVE AccessAllowed, BUILTIN\Administrators AccessAllowed, BUILTIN\Remote Management Users
AccessAllowed
Remoting Returns Deserialized Data
- The results you receive from a remote computer have been serialized into XML, and then deserialized on your computer.
- In essence, the objects placed into your shell’s pipeline are static, detached snapshots of what was on the remote computer at the time your command completed.
- These deserialized objects lack the methods of the originals objects, and instead only offer static properties.
- If you need to access methods or change properties, or in other words if you must work with the live objects, simply make sure you do so on the remote side, before the objects get serialized and travel back to the caller
PS C:\> $s = New-PSSession -ComputerName Server01
PS C:\> Import-Module -PSSession $s PSWorkflow
PS C:\> Get-Module
ModuleType Name ExportedCommands
---------- ---- ----------------
Manifest Microsoft.PowerShell.Management {Add-Computer, Add-Content, Checkpoint-Computer, Clear-Content...}
Manifest Microsoft.PowerShell.Utility {Add-Member, Add-Type, Clear-Variable, Compare-Object...}
Script PSScheduledJob {Add-JobTrigger, Disable-JobTrigger, Disable-ScheduledJob, Enable-Job...
The proxy commands look like the real commands, but they’re functions, NOT Cmdlets.
PS C:\> Get-Command -Module PSScheduledJob CommandType Name ModuleName ----------- ---- ---------- Function Add-JobTrigger PSScheduledJob Function Disable-JobTrigger PSScheduledJob Function Disable-ScheduledJob PSScheduledJob Function Enable-JobTrigger PSScheduledJob Function Enable-ScheduledJob PSScheduledJob Function Get-JobTrigger PSScheduledJob Function Get-ScheduledJob PSScheduledJob Function Get-ScheduledJobOption PSScheduledJob Function New-JobTrigger PSScheduledJob Function New-ScheduledJobOption PSScheduledJob Function Register-ScheduledJob PSScheduledJob Function Remove-JobTrigger PSScheduledJob Function Set-JobTrigger PSScheduledJob Function Set-ScheduledJob PSScheduledJob Function Set-ScheduledJobOption PSScheduledJob Function Unregister-ScheduledJob PSScheduledJob
Credits:
* terminating, non-terminating errors
* throw
* Write-error
* $ErrorActionVariable, -ErrorAction parameter
| SOAP | REST |
|---|---|
| SOAP stands for Simple Object Access Protocol | REST stands for Representational State Transfer |
| SOAP has been around a while | REST is a newcomer and fixes few problems with SOAP |
| Relies exclusively on XML | Can also use other smaller message/data formats like JSON, CSV or even RSS |
| Have to use XML for requests by making RPC calls, and response if received in XML as well | REST relies on a simple URL in many cases |
| Slow, requires bandwidth | Fast – lighter weight alternative |
| In-Built error handling | NA |
| SOAP is a protocol. SOAP was designed with a specification. It includes a WSDL (Web Service Definition Language) file which has the required information on what the web service does in addition to the location of the web service. | REST is an Architectural style in which a web service can only be treated as a RESTful service if it follows the constraints of being Client ,Server, Stateless, Cacheable, Layered System, Uniform Interface |
| SOAP cannot make use of REST since SOAP is a protocol and REST is an architectural pattern. | REST can make use of SOAP as the underlying protocol for web services, because in the end it is just an architectural pattern. |
| SOAP uses service interfaces to expose its functionality to client applications. In SOAP, the WSDL file provides the client with the necessary information which can be used to understand what services the web service can offer. | REST use Uniform Service locators to access to the components on the hardware device. |
| SOAP requires more bandwidth for its usage. Since SOAP Messages contain a lot of information inside of it, the amount of data transfer using SOAP is generally a lot. | REST does not need much bandwidth when requests are sent to the server. REST messages mostly just consist of JSON messages. Below is an example of a JSON message passed to a web server. You can see that the size of the message is comparatively smaller to SOAP. {“city”:”Mumbai”,”state”:”Maharastra”} |
| Tranfer on HTTP, FTP and SMTP etc | Only HTTP |
There are two types of architecture with DSC:
The configurations are sent/pushed manually towards one or more units that we call “node”. This action is done by an administrator.
Pull mode
A “Pull Server” is created and the nodes contact this server at regular intervals so as to obtain their configuration.
Items allowed to configure on the nodes, is called a DSC Resources. Run Get-DSCResource cmdlet to list all the DSC resources
PS C:\> Get-DscResource | select Name,Module,Properties | Ft -AutoSize
Name Module Properties
---- ------ ----------
File {DestinationPath, Attributes, Checksum, Contents...}
SignatureValidation {SignedItemType, TrustedStorePath}
PackageManagement PackageManagement {Name, AdditionalParameters, DependsOn, Ensure...}
PackageManagementSource PackageManagement {Name, ProviderName, SourceUri, DependsOn...}
Archive PSDesiredStateConfiguration {Destination, Path, Checksum, Credential...}
Environment PSDesiredStateConfiguration {Name, DependsOn, Ensure, Path...}
Group PSDesiredStateConfiguration {GroupName, Credential, DependsOn, Description...}
GroupSet PSDesiredStateConfiguration {DependsOn, PsDscRunAsCredential, GroupName, Ensure...}
Log PSDesiredStateConfiguration {Message, DependsOn, PsDscRunAsCredential}
Package PSDesiredStateConfiguration {Name, Path, ProductId, Arguments...}
ProcessSet PSDesiredStateConfiguration {DependsOn, PsDscRunAsCredential, Path, Credential...}
Registry PSDesiredStateConfiguration {Key, ValueName, DependsOn, Ensure...}
Script PSDesiredStateConfiguration {GetScript, SetScript, TestScript, Credential...}
Service PSDesiredStateConfiguration {Name, BuiltInAccount, Credential, Dependencies...}
ServiceSet PSDesiredStateConfiguration {DependsOn, PsDscRunAsCredential, Name, StartupType...}
User PSDesiredStateConfiguration {UserName, DependsOn, Description, Disabled...}
WaitForAll PSDesiredStateConfiguration {NodeName, ResourceName, DependsOn, PsDscRunAsCredential...}
WaitForAny PSDesiredStateConfiguration {NodeName, ResourceName, DependsOn, PsDscRunAsCredential...}
WaitForSome PSDesiredStateConfiguration {NodeCount, NodeName, ResourceName, DependsOn...}
WindowsFeature PSDesiredStateConfiguration {Name, Credential, DependsOn, Ensure...}
WindowsFeatureSet PSDesiredStateConfiguration {DependsOn, PsDscRunAsCredential, Name, Ensure...}
WindowsOptionalFeature PSDesiredStateConfiguration {Name, DependsOn, Ensure, LogLevel...}
WindowsOptionalFeatureSet PSDesiredStateConfiguration {DependsOn, PsDscRunAsCredential, Name, Ensure...}
WindowsPackageCab PSDesiredStateConfiguration {Ensure, Name, SourcePath, DependsOn...}
WindowsProcess PSDesiredStateConfiguration {Arguments, Path, Credential, DependsOn...}
DSC syntax contains 3 basic components –
- Configuration
- Node – Name of server/machine
- Resource (DSC Resource)
To view the DSC Configuraiton use the cmdlet: Get-DscResource <Name of Resource> -Syntax
Writing a simple Configuration
Configuration FileCopy # Name of the configuration
{
param( # Configuration parameters
[Parameter(Mandatory=$true)]
[String[]]$Servers,
[Parameter(Mandatory=$true)]
[String]$SourceFile,
[Parameter(Mandatory=$true)]
[String]$DestinationFile
)
Node $Servers # Node deploys the configuration on machine(s)
{
File 'CopyHostFile'
{
Ensure = "Present"
SourcePath = $SourceFile
DestinationPath = $DestinationFile
}
Service 'StartService'
{
Name = "Bits"
StartupType = "Manual"
State = "Running"
}
}
}
Following command will generate a MOF file, with name of the node, like localhost.mof
Following command will generate a MOF file, with name of the node, like localhost.mof
FileCopy -Servers localhost -SourceFile C:\test\out.txt -DestinationFile C:\test\filemov -OutputPath C:\test\mof -Verbose
Push the configuration using the .mof file
Start-DscConfiguration C:\test\mof\ -Verbose -wait
Checking past DSC Configuration
PS C:\> Get-DscConfigurationStatus Status StartDate Type Mode RebootRequested NumberOfResources ------ --------- ---- ---- --------------- ----------------- Success 8/15/2018 7:58:41 PM Initial PUSH False 2
Testing DSC Resource configuration with the MOF Files
PS C:\> Test-DscConfiguration -Path C:\test\mof\
PSComputerName ResourcesInDesiredState ResourcesNotInDesiredState InDesiredState
-------------- ----------------------- -------------------------- --------------
localhost {[File]CopyHostFile::[FileC... False