about_Logging_Non-Windows

Article
09/19/2022

Short description

PowerShell logs internal operations from the engine, providers, and cmdlets.

Long description

PowerShell logs details of PowerShell operations. For example, PowerShell will log operations such as starting and stopping the engine and starting and stopping providers. It will also log details about PowerShell commands.

The location of PowerShell logs is dependent on the target platform. On Linux, PowerShell logs to syslog and rsyslog.conf can be used. For more information, refer to the Linux computer's local man pages. On macOS, the os_log logging system is used. For more information, see os_log developer documentation.

Viewing PowerShell log output on Linux

PowerShell logs to syslog on Linux and any of the tools commonly used to view syslog contents may be used.

The format of the log entries uses the following template:

TIMESTAMP MACHINENAME powershell[PID]: (COMMITID:TID:CID)
  [EVENTID:TASK.OPCODE.LEVEL] MESSAGE

Field	Description
`TIMESTAMP`	A date/time when the log entry was produced.
`MACHINENAME`	The name of the system where the log was produced.
`PID`	The process ID of the process that wrote the log entry.
`COMMITID`	The `git commit` ID or tag used to produce the build.
`TID`	The thread ID of the thread that wrote the log entry.
`CID`	The hex channel identifier of the log entry.
	10 = Operational, 11 = Analytic
`EVENTID`	The event identifier of the log entry.
`TASK`	The task identifier for the event entry
`OPCODE`	The opcode for the event entry
`LEVEL`	The log level for the event entry
`MESSAGE`	The message associated with the event entry

Note

EVENTID, TASK, OPCODE, and LEVEL are the same values as used when logging to the Windows event log.

Filtering PowerShell log entries using rsyslog

Normally, PowerShell log entries are written to the default location/file for syslog. However, it's possible to redirect the entries to a custom file.

Create a conf for PowerShell log configuration and provide a number that's less than 50 (for 50-default.conf), such as 40-powershell.conf. The file should be placed under /etc/rsyslog.d.

Add the following entry to the file:

:syslogtag, contains, "powershell[" /var/log/powershell.log
& stop

Make sure /etc/rsyslog.conf includes the new file. Often, it will have a generic include statement that looks like following configuration:

$IncludeConfig /etc/rsyslog.d/*.conf

If it doesn't, you'll need to add an include statement manually.

Make sure attributes and permissions are set appropriately.

-rw-r--r-- 1 root root   67 Nov 28 12:51 40-powershell.conf

Set ownership to root.

chown root:root /etc/rsyslog.d/40-powershell.conf

Set access permissions: root has read/write, users have read.
```
chmod 644 /etc/rsyslog.d/40-powershell.conf
```

Viewing PowerShell log output on macOS

The easiest method for viewing PowerShell log output on macOS is using the Console application.

Search for the Console application and launch it.
Select the Machine name under Devices.
In the Search field, enter pwsh for the PowerShell main binary.
Change the search filter from Any to Process.
Perform the operations.
Optionally, save the search for future use.

To filter on a specific process instance of PowerShell in the Console, the variable $pid contains the process ID.

Enter the pid (Process ID) in the Search field.
Change the search filter to PID.
Perform the operations.

Viewing PowerShell log output from a command line

The log command can be used to view PowerShell log entries from the command line.

sudo log stream --predicate 'process == "pwsh"' --info

Persisting PowerShell log output

By default, PowerShell uses the default memory-only logging on macOS. This behavior can be changed to enable persistence using the log config command.

The following script enables info level logging and persistence:

log config --subsystem com.microsoft.powershell --mode=persist:info,level:info

The following command reverts PowerShell logging to the default state:

log config --subsystem com.microsoft.powershell --mode=persist:default,level:default

After persistence is enabled, the log show command can be used to export log items. The command provides options for exporting the last N items, items since a given time, or items within a given time span.

For example, the following command exports items since 9am on April 5 of 2018:

log show --info --start "2018-04-05 09:00:00" --predicate "process = 'pwsh'"

You can get help for log by running log show --help for additional details.

Tip

When executing any of the log commands from a PowerShell prompt or script, use double quotes around the entire predicate string and single quotes within. This avoids the need to escape double quote characters within the predicate string.

You may also want to consider saving the event logs to a more secure location such as a central event log collector, or SIEM aggregator. You can set up SIEM in Azure. For more information, see Generic SIEM integration.

Configuring logging on a non-Windows system

On Windows, logging is configured by creating ETW trace listeners or by using the Event Viewer to enable Analytic logging. On Linux and macOS, logging is configured using the file powershell.config.json. The rest of this section will discuss configuring PowerShell logging on a non-Windows system.

By default, PowerShell enables informational logging to the operational channel. What this means is any log output produced by PowerShell that is marked as operational and has a log (trace) level greater than informational will be logged. Occasionally, diagnoses may require additional log output, such as verbose log output or enabling analytic log output.

The file powershell.config.json is a JSON formatted file residing in the PowerShell $PSHOME directory. Each installation of PowerShell uses its own copy of this file. For normal operation, this file is left unchanged. Although it can be useful, to change some of the settings in the file, for diagnosis or for distinguishing between multiple PowerShell versions on the same system or even multiple copies of the same version (See LogIdentity in the table below).

The following code is an example configuration:

{
  "Microsoft.PowerShell:ExecutionPolicy": "RemoteSigned",
  "PowerShellPolicies": {
    "ScriptExecution": {
      "ExecutionPolicy": "RemoteSigned",
      "EnableScripts": true
    },
    "ScriptBlockLogging": {
      "EnableScriptBlockInvocationLogging": true,
      "EnableScriptBlockLogging": true
    },
    "ModuleLogging": {
      "EnableModuleLogging": false,
      "ModuleNames": [
        "PSReadline",
        "PowerShellGet"
      ]
    },
    "ProtectedEventLogging": {
      "EnableProtectedEventLogging": false,
      "EncryptionCertificate": [
        "Joe"
      ]
    },
    "Transcription": {
      "EnableTranscripting": true,
      "EnableInvocationHeader": true,
      "OutputDirectory": "F:\\tmp\\new"
    },
    "UpdatableHelp": {
      "DefaultSourcePath": "f:\\temp"
    },
    "ConsoleSessionConfiguration": {
      "EnableConsoleSessionConfiguration": false,
      "ConsoleSessionConfigurationName": "name"
    }
  },
  "LogLevel": "verbose"
}

The properties for configuring PowerShell logging are listed in the following table. Values marked with an asterisk, such as Operational*, indicate the default value when no value is provided in the file.

Property	Values	Description
`LogIdentity`	(string name)	The name to use when logging. By default,
	powershell*	powershell is the identity. This value can be
		used to tell the difference between two
		instances of a PowerShell installation, such
		as a release and beta version. This value is
		also used to redirect log output to a
		separate file on Linux. See the discussion of
		rsyslog above.
`LogChannels`	Operational*	The channels to enable. Separate the values
	Analytic	with a comma when specifying more than one.
`LogLevel`	Always	Specify a single value. The value enables
	Critical	itself and all values above it in the
	Error	list to the left.
	Warning
	Informational*
	Verbose
	Debug
`LogKeywords`	Runspace	Keywords provide the ability to limit logging
	Pipeline	to specific components within PowerShell. By
	Protocol	default, all keywords are enabled and change
	Transport	this value is only useful for very
	Host	specialized troubleshooting.
	Cmdlets
	Serializer
	Session
	ManagedPlugin

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