+### From 3.4.1 to 4.0.0
+
+You may have to change your administrator password in your config file as admin password are only stored using sha256 (SHA2).
+To do so, edit `lib/config.local.php` and update `admin_password` option using `echo -n MyNewPassw0rd | sha256sum` command.
+
+Subfolder division changed in Jirafeau storage. You can either start from a fresh `var-` folder or you need to migrate your data.
+
+In order to migrate your existing data:
+1. Be sure to have a working backup of your Jirafeau instance and/or the rest of your hosting before any operation
+2. Go to `var-` folder
+3. Be sure you have read and write permissions on files and folders with your current user
+4. Run the following commands:
+```bash
+# Migrate files folder
+find files -type f ! -name "*_count" | while read f; do bn="$(basename "$f")"; dst="files/${bn:0:8}/${bn:8:8}/${bn:16:8}/${bn:24:8}/"; mkdir -p "$dst"; mv "$f" "$dst" ; mv "${f}_count" "$dst"; done; find files -maxdepth 1 -type d -iname "?" -exec rm -rf {} \;
+# Migrate links folder
+find links -type f | while read link; do bn="$(basename "$link")"; mkdir "links/$bn"; mv "$link" "links/$bn/"; done; find links -maxdepth 1 -type d -iname "?" -exec rm -rf {} \;
+```
+
+### From 4.0.0 to 4.1.1
+
+There is nothing special to do to update from/to the following versions:
+- 4.0.0 -> 4.1.0
+- 4.1.0 -> 4.1.1
+