WSL

WSL, or Windows Subsystem for Linux, is a feature of Windows that allows you to run a Linux environment on your Windows machine, without the need for a separate virtual machine or dual booting. WSL is designed to provide a seamless and productive experience for developers who want to use both Windows and Linux at the same time

Enable WSL

1. Open PowerShell as Admin: Press Win + X and select "Terminal (Admin)" or "Windows PowerShell (Admin)".
2. Install WSL: Type wsl --install and press Enter. This command enables required features, installs the latest kernel, and defaults to Ubuntu.
3. Restart: Your computer will likely need to restart to complete the installation.
4. Optional : Create User: After reboot, a terminal window will open asking for a Linux username and password (these are separate from your Windows login).

Basic Usage

• Launch: Open the Start Menu and search for your installed distro (e.g., "Ubuntu") or type wsl in Command Prompt/PowerShell.
• Update Software: In your Linux terminal, run sudo apt update && sudo apt upgrade (for Ubuntu/Debian).
• Install Software: Use sudo apt install <package_name> (e.g., sudo apt install git).
• Access Windows Files: Your Windows drives are mounted under /mnt/ (e.g., cd /mnt/c/Users/YourUser).

WSL commands

#WSL check status 
>wsl -l -v 

# Start WSL machine 
>wsl -d <machine name>

# Stop a WSL machine 
>wsl -t <machine name>

# Stop all WSL machine
>wsl --shutdown

Enable windows ping response

# as Admin Powershell
Set-NetFirewallRule -Name CoreNet-Diag-ICMP4-EchoRequest-In -enabled True

WSL Networking

Networking in WSL can be configured in various ways to enable communication between Windows and Linux applications.

Default Networking Mode: NAT

By default, WSL uses a NAT (Network Address Translation) based architecture. This means that the Linux distribution running under WSL has its own IP address, separate from the Windows host. To access a Linux networking app from Windows, you can use localhost. Conversely, to access a Windows networking app from Linux, you need to use the IP address of the Windows host.

Identifying IP Addresses

From Windows to Linux: To find the IP address of a Linux distribution running via WSL2, use the command:

wsl -d <DistributionName> hostname -I

From Linux to Windows: To find the IP address of the Windows host from a Linux distribution, use the command:

ip route show | grep -i default | awk '{ print $3}'

Mirrored Mode Networking

On machines running Windows 11 22H2 and higher, you can enable mirrored mode networking by setting networkingMode=mirrored under [wsl2] in the .wslconfig file at C:\Users\<username> folder. This mode mirrors the network interfaces from Windows into Linux, allowing for improved compatibility and new features.

Benefits of Mirrored Mode

• IPv6 Support: Enables IPv6 connectivity.
• Localhost Access: Allows connecting to Windows servers from within Linux using localhost (127.0.0.1).
• VPN Compatibility: Improved networking compatibility for VPNs.
• Multicast Support: Enables multicast networking.
• LAN Access: Allows connecting to WSL directly from your local area network (LAN).

Accessing Applications

From Windows to Linux

To access a Linux networking app from Windows, you can use localhost as the destination address. For example, if you have a Node.js server running on Linux, you can access it from a Windows browser using http://localhost:3000.

From Linux to Windows

To access a Windows networking app from Linux, you need to use the IP address of the Windows host. For example, to connect to a Node.js server running on Windows, you can use the following command in Linux:

curl http://<WindowsHostIP>:3000

Advanced Configuration

You can configure advanced networking settings using the wsl.conf and .wslconfig files.

• wsl.conf file is used for per-distribution settings,
• .wslconfig file is used for global settings across all WSL distributions.

Example .wslconfig File : This configuration enables mirrored mode networking, DNS tunneling, and automatic proxy settings

[wsl2]

networkingMode=mirrored

dnsTunneling=true

autoProxy=true

By understanding and configuring these networking options, you can optimize the communication between your Windows and Linux applications running under WSL.

WSL machine network configuration

$ cat /etc/wsl.conf

$ cat /etc/wsl-distribution.conf

Remote Connection to WSL

To login into WSL from remote,

• Enable OpenSSH package on Windows host . (we also can use GUI windows through quickly launch the GUI with optionalfeatures or appwiz.cpl)

#check available OpenSSH service  
PS C:> Get-WindowsCapability -Online | Where-Object Name -like 'OpenSSH*'
Name  : OpenSSH.Client~~~~0.0.1.0
State : NotPresent

Name  : OpenSSH.Server~~~~0.0.1.0
State : NotPresent

# Install the OpenSSH Client
Add-WindowsCapability -Online -Name OpenSSH.Client~~~~0.0.1.0

# Install the OpenSSH Server
Add-WindowsCapability -Online -Name OpenSSH.Server~~~~0.0.1.0

# Reboot system and do following commands on powershell 

# Start the sshd service
Start-Service sshd

# OPTIONAL but recommended:
Set-Service -Name sshd -StartupType 'Automatic'

# Confirm the Firewall rule is configured. It should be created automatically by setup. Run the following to verify
if (!(Get-NetFirewallRule -Name "OpenSSH-Server-In-TCP" -ErrorAction SilentlyContinue)) {
    Write-Output "Firewall Rule 'OpenSSH-Server-In-TCP' does not exist, creating it..."
    New-NetFirewallRule -Name 'OpenSSH-Server-In-TCP' -DisplayName 'OpenSSH Server (sshd)' -Enabled True -Direction Inbound -Protocol TCP -Action Allow -LocalPort 22
} else {
    Write-Output "Firewall rule 'OpenSSH-Server-In-TCP' has been created and exists."
}

• Next, set up SSH for each WSL instance. Here, I use a different port number for each instance.
• todo

$ sudo apt install openssh-server