docs: Add troubleshooting on ENOSPC

Closes facebook#7612

Author: huchenme

docusaurus/docs/troubleshooting.md

@@ -20,6 +20,24 @@ If this doesn’t happen, try one of the following workarounds:
 
 If none of these solutions help please leave a comment [in this thread](https://github.com/facebook/create-react-app/issues/659).
 
+## `npm start` fail due to watch error
+
+If you are using Linux system and see error similar to this: `ENOSPC: System limit for number of file watchers reached`.
+
+If you are running Debian, RedHat, or another similar Linux distribution, run the following in a terminal:
+
+```sh
+echo fs.inotify.max_user_watches=524288 | sudo tee -a /etc/sysctl.conf && sudo sysctl -p
+```
+
+If you are running ArchLinux, run the following command instead:
+
+```sh
+echo fs.inotify.max_user_watches=524288 | sudo tee /etc/sysctl.d/40-max-user-watches.conf && sudo sysctl --system
+```
+
+Then paste it in your terminal and press on enter to run it. You could find more information [here](https://github.com/guard/listen/wiki/Increasing-the-amount-of-inotify-watchers#the-technical-details).
+
 ## `npm test` hangs or crashes on macOS Sierra
 
 If you run `npm test` and the console gets stuck after printing `react-scripts test` to the console there might be a problem with your [Watchman](https://facebook.github.io/watchman/) installation as described in [facebook/create-react-app#713](https://github.com/facebook/create-react-app/issues/713).