Merge pull request #1532 from hedgedoc/docs/faq

docs/content/faq.md

@@ -0,0 +1,60 @@
+# FAQ
+
+This page collects Frequently Asked Questions of the community.  
+If you have any questions that aren't answered here, feel free to ask us on [Matrix][matrix.org-url] or stop by our [community forums][hedgedoc-community].
+
+[matrix.org-url]: https://chat.hedgedoc.org
+[hedgedoc-community]: https://community.hedgedoc.org
+
+## Why is CodiMD now called HedgeDoc?
+The short version: There were two CodiMD-projects on GitHub, the community-driven fork and the original project maintained by the HackMD-team.
+To solve this naming conflict, our community-driven version was renamed to HedgeDoc.
+For a full writeup, check out the [history overview](https://hedgedoc.org/history/).
+
+
+## Can I run multiple instances on the same database?
+No. The HedgeDoc server process is not entirely stateless and therefore running more than one instance will result in missing/broken content for users.
+In order to solve issues like HA-capabilities, please use a high level orchestrator that makes sure that always 1 instance is running on your infrastructure and that the database is available.
+The server process usually starts within seconds and therefore the possible downtime should be minimal.
+
+
+## Why was the PDF Export feature removed?
+We used a headless Chromium instance to generate the PDFs, but that led to some security vulnerabilities and was therefore deactivated.
+There are currently plans to re-add this feature in a safe way, but this will most likely take some time and can be expected at the earliest with HedgeDoc 2.1 (but could also take longer).  
+In the meantime you can use your browsers print to PDF Feature.
+This [page](https://www.digitaltrends.com/computing/how-to-save-a-webpage-as-a-pdf/) explains how to do that for multiple browsers.
+
+
+## Why can't I embed some PDFs?  
+Many servers don't allow the embedding of their content on arbitrary sites.
+
+For a more technical explanation:  
+The `X-Frame-Options` header can be used to specify if a given webpage can be embedded.
+For security reasons this header is often set to `SAMEORIGIN`, which disallows embedding on other origins.
+To be able to embed a PDF inside a HedgeDoc note, the server that hosts the PDF must either send no `X-Frame-Options`
+header (which might be insecure) or include the URI of your HedgeDoc instance in an `ALLOW-FROM` statement.
+See [Mozillas docs](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Frame-Options) for more details.  
+Also note that the `X-Frame-Options` header [is being obsoleted](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/frame-ancestors)
+by the `frame-ancestors` statement in the `Content-Security-Policy` header.
+
+## Why can't I embed a HedgeDoc note in other pages using iframes?
+Allowing your HedgeDoc instance to be embedded in other pages increases the risk of [clickjacking](https://en.wikipedia.org/wiki/Clickjacking),
+[XSS](https://en.wikipedia.org/wiki/Cross-site_scripting) and other attacks.
+Therefore, **we recommend to not enable** this option.  
+If you still want to allow embedding via iframe, ensure that:
+
+- Your HedgeDoc instance is served via HTTPS
+- `cookiePolicy` / `CMD_COOKIE_POLICY` is set to `none` (Otherwise you will get a `AUTH failed: No cookie transmitted` error.)
+- `csp.allowFraming` / `CMD_CSP_ALLOW_FRAMING` is set to `true`
+
+See also the [configuration docs](/configuration/#web-security-aspects) for more information about these options.
+
+## I can't upload images or the upload gets stuck
+This problem is typically accompanied by the error `Invalid URL: /uploads/` in the log and is often caused by a missing
+`domain` / `CMD_DOMAIN` config option or an incorrect reverse proxy config.  
+Have a look at our [reverse proxy documentation](https://docs.hedgedoc.org/guides/reverse-proxy/)
+and make sure that `protocolUseSSL` / `CMD_PROTOCOL_USESSL` is set to `true` if you serve HedgeDoc via HTTPS.
+
+## HedgeDoc fails executing migrations and does not start
+Unfortunately, older versions of HedgeDoc had some bugs regarding migrations and didn't always record that a migration was executed.  
+Have a look at the *[Troubleshooting Migrations](/guides/migration-troubleshooting/)* guide for more information.

docs/content/index.md

@@ -15,6 +15,6 @@ If you have any questions that aren't answered here, feel free to ask us on [Mat
 
 [hedgedoc-demo]: https://demo.hedgedoc.org
 [hedgedoc-history]: https://hedgedoc.org/history
-[hedgedoc-faq]: https://hedgedoc.org/faq
+[hedgedoc-faq]: /faq
 [matrix.org-url]: https://chat.hedgedoc.org
 [hedgedoc-community]: https://community.hedgedoc.org

docs/mkdocs.yml

@@ -48,7 +48,7 @@ nav:
       - 'Operational Transformation': dev/ot.md
       - Webpack: dev/webpack.md
       - 'Documentation': dev/documentation.md
-  - FAQ: https://hedgedoc.org/faq
+  - FAQ: faq.md
 markdown_extensions:
   - toc:
       permalink: true