Running Linux Commands within Windows Using WSL

In the first chapter of Cybersecurity Ops with bash we go over some of the ways you can leverage the power of the Linux command line directly from the Windows environment.

One of my favorite ways of doing this is by using the Windows Subsystem for Linux or WSL.

WSL was introduced as part of Windows 10, and it allows you to run an emulated or virtualized version of Linux natively within Windows.

There are several Linux distributions to choose from including Ubuntu and Kali.

How to Install WSL in Windows 10

In order to use WSL you will first need to install it.

1. Using the Windows Start Menu, search for "Windows Features"

2. Select "Turn Windows features on or off"

Turn On Windows Feature

3. Check the box next to "Windows Subsystem for Linux" and select "OK"

Enable the Windows Subsystem for Linux

4. After the installation completes select "Restart now"

5. Once the system is restarted use the Windows Start Menu to search for "Microsoft Store"

6. In the Microsoft Store, search for "Linux" and select the Linux distribution you would like to install

Microsoft Store

7. Click the "Install" button and then "Get"

Install Ubuntu

8. After the Linux distribution is done installing click the "Launch" button.

You are now ready to start using the Windows Subsystem for Linux!

For more advance directions and troubleshooting see Microsoft's instructions.

How to Run WSL

Once the Windows Subsystem for Linux is enabled and you have installed a Linux distribution you can start it by opening the Windows Command Prompt and typing wsl

C:\>wsl

Welcome to Ubuntu 20.04.2 LTS (5.4.72-microsoft-standard-WSL2 x86_64)
$

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Error Message - No Installed Distributions

Sometimes when running WSL for the first time you may receive the following error:

C:\>wsl

Windows Subsystem for Linux has no installed distributions.
Distributions can be installed by visiting the Microsoft Store:

To resolve this, perform a search using the Windows Start Menu for the name of the Linux distribution you installed from the Microsoft Store. For example, search for "Ubuntu":

Launch WSL Ubuntu Instance

Click the program to launch it and that should finish the installation on your system. You should not longer receive the error message when running wsl from the Command Prompt.

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Once inside the WSL Linux distribution you can do things you normally would such as run Linux commands and install packages.

Running Linux Commands from Within WSL

You can also directly run Linux commands from the Windows Command Prompt by using the wsl command and providing the Linux command as an argument. The command will execute in the WSL Linux distribution and the results will be returned back to the Windows command prompt.

In the example below you can see the Linux cowsay command run directly from the Windows Command Prompt:

Running Linux Commands from the Windows Command Prompt

Note that you must precede the Linux command with wsl, if you do not you will receive an error. Here is the incorrect method:

C:\>grep

'grep' is not recognized as an internal or external command,
operable program or batch file.

And here is the correct method:

C:\>wsl grep

Usage: grep [OPTION]... PATTERNS [FILE]...
Try 'grep --help' for more information.

Piping and Redirection

You can also use input/output piping and redirection when using the wsl command, but you need to be careful how you do it to ensure it occurs within the correct operating system environment. Let's see what happens if you run the following command pipeline from the Windows command prompt:

C:\>wsl ps -e | grep ps

'grep' is not recognized as an internal or external command,
operable program or batch file.

Note that the output states that the grep command is not recognized. That is because Windows executes the ps -e command from within the WSL environment, but then returns the result back to the Windows environment. Windows then tries to pipe that output into the grep command, which of course does not exist in the Windows environment. To overcome this, simply add the wsl command again after the pipe so the grep command runs in the Linux environment.

C:\>wsl ps -e | wsl grep ps
    7 tty1     00:00:00 ps

I/O redirection works the same way. Here is an example:

C:\>wsl ps -e > ps.txt

Here the ps -e command is executed in the Linux environment using wsl and the results are returned to the Windows environment. Windows then redirects the output to the file ps.txt.

WSL and Windows PowerShell

Running Linux Commands from PowerShell

Running WSL works exactly the same way from the Windows PowerShell. That means you are able to access your favorite Linux commands, bash scripts, and programs from directly within PowerShell scripts!

WSL 2

In mid-2020 Microsoft released WSL version 2. WSL 2 provides a more full-featured virtualized environment allowing for complete access to system calls. That means you can now install the complete array of Linux applications including Docker and similar programs.

Recent releases of WSL also supports running Linux programs that have graphical user interfaces.

Links and Resources

• Installing WSL

• Command reference for Windows Subsystem for Linux

• WSL Version 2