Add docs for migration

docs/i_u_m_migration.md

@@ -0,0 +1,39 @@
+If you want to migrate your old mailcow installation to a new server you can follow this:
+
+**1\.** 
+Install [Docker](https://docs.docker.com/engine/installation/linux/) and [Docker Compose](https://docs.docker.com/compose/install/) on your new server.
+
+Quick installation for most operation systems:
+
+- Docker
+```
+curl -sSL https://get.docker.com/ | CHANNEL=stable sh
+# After the installation process is finished, you may need to enable the service and make sure it is started (e.g. CentOS 7)
+systemctl enable docker.service
+```
+
+- docker-compose
+```
+curl -L https://github.com/docker/compose/releases/download/$(curl -Ls https://www.servercow.de/docker-compose/latest.php)/docker-compose-$(uname -s)-$(uname -m) > /usr/local/bin/docker-compose
+chmod +x /usr/local/bin/docker-compose
+```
+
+Please use the latest Docker engine available and do not use the engine that ships with your distros repository.
+
+**2\.** Make sure that Docker is stopped:
+```
+systemctl status docker.service
+```
+    
+**3\.**	Run the following commands on the source machine (take care of adding the trailing slashes in the first path parameter as shown below!):
+```
+rsync -aHhP --numeric-ids --delete /opt/mailcow-dockerized/ root@some.other.machine.net:/opt/mailcow-dockerized
+rsync -aHhP --numeric-ids --delete /var/lib/docker/volumes/ root@some.other.machine.net:/var/lib/docker/volumes
+```
+
+**4\.**    Shut down Mailcow via `docker-compose down` and stop Docker on the source machine.
+**5\.**    Repeat step 3 with the same commands (this will be much quicker than the first time).
+**6\.**    Start docker on the target machine `systemctl start docker.service`.
+**7\.**    Go into the /opt/mailcow-dockerized directory and run `docker-compose pull`.
+**8\.**    Start the whole mailcow stack with `docker-compose up -d` and everything should be fine.
+**9\.**    Change your DNS settings.

mkdocs.yml

@@ -1,6 +1,6 @@
 site_name: "mailcow: dockerized documentation"
 site_url: https://mailcow.github.io/mailcow-dockerized-docs/
-copyright: 'Copyright © 2018 André Peters'
+copyright: 'Copyright © 2019 André Peters'
 repo_name: mailcow/mailcow-dockerized
 repo_url: https://github.com/mailcow/mailcow-dockerized
 edit_uri: ../mailcow-dockerized-docs/edit/master/docs/
@@ -24,9 +24,10 @@ nav:
 - 'Prerequisites':
   - 'Prepare Your System': 'prerequisite-system.md'
   - 'DNS Setup': 'prerequisite-dns.md'
-- 'Installation & Update':
-  - 'Installation': 'install.md'
-  - 'Update': 'install-update.md'
+- 'Installation, Update & Migration':
+  - 'Installation': 'i_u_m_install.md'
+  - 'Update': 'i_u_m_update.md'
+  - 'Migration': 'i_u_m_migration.md'
 - 'First Steps (optional)':
   - 'SSL': 'firststeps-ssl.md'
   - 'Rspamd Web UI': 'firststeps-rspamd_ui.md'