Merge pull request #4246 from cypress-io/wsl2

Add WSL2 installation instructions

Author: cowboy

assets/img/guides/rule-application-selection.png

@@ -9,6 +9,7 @@ title: Installing Cypress
 - How to install Cypress via `npm`
 - How to install Cypress via direct download
 - How to version and run Cypress via `package.json`
+- How to run Cypress on `wsl2` in windows
 
 </Alert>
 
@@ -515,3 +516,76 @@ Notes on pre-releases:
   release over a pre-release - if you have a pre-release of Cypress vX.Y.Z
   installed, the official release of Cypress vX.Y.Z will not install until you
   do `cypress cache clear`.
+
+### Windows Subsystem for Linux
+
+#### WSL2
+
+First, install the prerequisite packages using the command that relates to your
+linux distribution ([Ubuntu/Debian](#Ubuntu-Debian) or [CentOS](#CentOS)).
+
+We need to have an [X-server](https://en.wikipedia.org/wiki/X.Org_Server) to
+display the Cypress UI from the linux subsystem. There are a variety of
+X-servers available, here we are going to use VcXsrv, you can use any other
+similar tool.
+
+Download [VcXsrv](https://sourceforge.net/projects/vcxsrv/) and install. You can
+set the settings to your preference ("Multiple windows" and "Start no client"
+are recommended), but on the page that lets you enable extra settings, be sure
+to select "Disable access control" which is required as WSL2 has its own IP
+address, which changes often.
+
+<DocsImage src="/img/guides/vcxsrv-extra-settings.png" alt="Disable access control in vcxsrv" ></DocsImage>
+
+In your `.bashrc` (or equivalent such as `.zshrc`) set the `DISPLAY` environment
+variable.
+
+```shell
+# set DISPLAY variable to the IP automatically assigned to WSL2
+export DISPLAY=$(cat /etc/resolv.conf | grep nameserver | awk '{print $2; exit;}'):0.0
+```
+
+To confirm `DISPLAY` variable has been set, print it out in the terminal. You
+may need to restart your terminal to see this change.
+
+```shell
+echo $DISPLAY
+# something like 172.17.224.1:0.0
+```
+
+The VcXsrv GUI uses [D-Bus](https://www.freedesktop.org/wiki/Software/dbus/) to
+internally communicate. After the `export DISPLAY` line in your `.bashrc`, add
+the following:
+
+```shell
+sudo /etc/init.d/dbus start &> /dev/null
+```
+
+Now your user needs to be granted access to run `sudo dbus` without needing to
+enter a password. To do so, use the `visido` command:
+
+```shell
+sudo visudo -f /etc/sudoers.d/dbus
+```
+
+In the editor that launches, add the following line, replacing `<your_username>`
+with your username (you can use the `whoami` command to print your username if
+you don't know it).
+
+```
+<your_username> ALL = (root) NOPASSWD: /etc/init.d/dbus
+```
+
+Go to Control Panel > System and Security > Windows Defender Firewall > Inbound
+Rules > New Rule.
+
+<DocsImage src="/img/guides/windows-firewall-disable-vcxsrv.png" alt="Add rule to allow connections for vcxsrv" ></DocsImage>
+
+Select Program and click on next. On the This program path, browse and select
+path to VcxSrv. On the next page select allow the connection and click next. On
+the next page, select all three options (Domain, Private, Public).
+
+<DocsImage src="/img/guides/rule-application-selection.png" alt="Select inbound rule application cases for vcxsrv" ></DocsImage>
+
+Give the rule a suitable name and description and click finish. WSL2 should now
+be able to open a GUI from shell.