Add migration page

1to2.md

@@ -1,5 +1,79 @@
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 layout: page
-title: Migration from 1.x to 2.0
+title: Migration from 1.x.x to 2.0.x
 permalink: /1to2/
 ---
+
+## Why a Migration?
+
+Radicale 2.0.x is different from 1.x.x, here's everything you need to know about
+this! **Please read this page carefully if you want to update Radicale.**
+
+You'll also find extra information
+in [issue #372](https://github.com/Kozea/Radicale/issues/372).
+
+### Python 3 Only
+
+Radicale 2.0.x works with Python >= 3.3, and **doesn't work anymore with
+Python 2**.
+
+(No, Python 3.3 is not new, it's been released more than 4 years ago.
+Debian stable provides Python 3.4.)
+
+### Dependencies
+
+Radicale now depends on [VObject](https://eventable.github.io/vobject/), a
+"full-featured Python package for parsing and creating iCalendar and vCard
+files". That's the price to pay to correctly read crazy iCalendar files and
+**support date-based filters, even on recurring events**.
+
+### Storage
+
+Calendars and address books are stored in a different way between 1.x.x and 2.0.x
+versions. **Launching 2.0.x without migrating your collections first will not
+work, Radicale won't be able to read your previous data.**
+
+There's now only one way to store data in Radicale: collections are stored as
+folders and events / contacts are stored in files. This new storage is close to
+the `multifilesystem`, but **it's now thread-safe, with atomic writes and file
+locks**.
+
+Migrating your data can be done with tool called
+[transplant](https://github.com/Kozea/transplant/blob/master/transplant.py)
+that will copy your collections from one server to another using
+CalDAV / CardDAV requests. Following these simple steps will help you migrate
+your data:
+
+- Stop Radicale 1.x.x,
+- edit your configuration to only listen to `http://localhost:5232`,
+- remove authentication,
+- restart the 1.x.x server,
+- download Radicale 2.0.x and go into the downloaded folder,
+- launch Radicale 2.0.x with
+  `python3 radicale.py --config=/dev/null --hosts=localhost:5233 --storage-filesystem-folder=~/.local/share/radicale/`,
+- download transplant and go into the downloaded folder,
+- launch transplant with `python3 transplant http://localhost:5232 http://localhost:5233`,
+- you're done!
+
+This migration should work at least with simple configurations of Radicale 1.x.x
+on Linux and macOS. Please adapt these steps carefully if you're on Windows or
+if you're using a more complex configuration.
+
+Other storage types can be used by creating [plugins](/plugins/). These storage
+types can reuse the current storage class to extend it (for example to add
+versioning) or can be totally different from it (yes, don't worry, you can
+write your own storage plugin using a DataBase®™ if you want).
+
+### Authentication
+
+**Radicale 2.0.x only provides htpasswd authentication out-of-the-box.** Other
+authentication methods can be added by creating or using [plugins](/plugins/).
+
+### Rights
+
+In Radicale 2.0.x, rights are managed using regex-based rules based on the
+login of the authenticated user and the URL of the resource. Default
+configurations are built in for common cases, you'll find more about this on
+the [Authentication & Rights](/rights/) page.
+
+Other rights managers can be added by creating [plugins](/plugins/).