Adds a few steps for migration from the LinuxServer.io image

docs/setup.rst

@@ -634,6 +634,48 @@ Migration to paperless-ngx is then performed in a few simple steps:
 10.  Optionally, follow the instructions below to migrate your existing data to PostgreSQL.
 
 
+Migrating from LinuxServer.io Docker Image
+========================
+
+As with any upgrades and large changes, it is highly recommended to create a backup before
+starting.  This assumes the image was running using Docker Compose, but the instructions
+are translatable to Docker commands as well.
+
+1.  Stop and remove the paperless container
+2.  If using an external database, stop the container
+3.  Update Redis configuration
+
+    a)  If ``REDIS_URL`` is already set, change it to ``PAPERLESS_REDIS`` and continue
+        to step 3.
+    b)  Otherwise, in the ``docker-compose.yml`` add a new service for Redis,
+        following `the example compose files <https://github.com/paperless-ngx/paperless-ngx/tree/main/docker/compose>`
+    b)  Set the environment variable ``PAPERLESS_REDIS`` so it points to the new Redis container
+
+4.  Update user mapping
+
+    a)  If set, change the environment variable ``PUID`` to ``USERMAP_UID``
+    b)  If set, change the environment variable ``PGID`` to ``USERMAP_GID``
+
+5.  Update configuration paths
+
+    a) Set the environment variable ``PAPERLESS_DATA_DIR``
+       to ``/config``
+
+6.  Update media paths
+
+    a) Set the environment variable ``PAPERLESS_MEDIA_ROOT``
+       to ``/data``
+
+7.  Update timezone
+
+    a) Set the environment variable ``PAPERLESS_TIME_ZONE``
+       to the same value as ``TZ``
+
+8.  Modify the ``image:`` to point to ``ghcr.io/paperless-ngx/paperless-ngx:latest`` or
+    a specific version if preferred.
+
+9.  Start the containers as before, using ``docker-compose``.
+
 .. _setup-sqlite_to_psql:
 
 Moving data from SQLite to PostgreSQL