La solution est ici https://forum.synology.com/enu/viewtopic.php?f=62&t=83269&start=15
après avoir essayé toute la première page de solution sans résultat
voici celle (en page 2) qui a fonctionné pour moi
Edit the group "users", on the "permissions" tab, choose "custom" for "homes".
You will need 2 entries here. First, the user needs to be able to "traverse" the "homes" folder to get to their own "home" folder without seeing all the other users. For that, set the following entry:
User Or Group: Everyone
Inherit From: <none>
Type: Allow
Apply To: All
Check "Traverse Folders/Execute Files"
Don't check anything else here!!!
Now, we need to add a second custom entry here to allow the user to read and edit their own files so use this:
User Or Group: Owner
Inherit From: <none>
Type: Allow
Apply To: Child folders, Child files, All descendants
Check "Read" (and everything under it)
Check "Write" (and everything under it)
The key is to remember that a user's "home" folder is actually a child folder of the shared "homes" folder.
Also, be sure that each user is the "owner" of all the files in their own "home". This should be the default for what they create but if you copy files to the user to get them started, you may need to change the properties of those files/folders so that the user owns them.
Finally under the "general properties" of the "homes" shared folder, I have checked both of the following items:
Hide this shared folder in "My Network Places"
Hide sub-folders and files from users without permissions