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