Set up a Synology shared folder and fix container permissions
Find the real DSM volume path, create a dedicated app folder, and trace Container Manager permission errors without widening access to your whole NAS.
Eugene Gavrilov
4 min read- NAS & storage
Your container needs a place to keep files on the NAS. A shared folder is a top-level DSM storage location that lives on a volume. Give the app its own subfolder and record the full path. If the app later reports a write error, check the mapping and the permissions independently.
Create a share and find its volume
- Open Control Panel → Shared Folder as a DSM administrator. Check for the share your app guide expects. If it already exists, select it and check its volume before reusing it.
- If you need a new share, choose Create → Create Shared Folder, give it a name and select the volume. Review the wizard and grant access to the accounts that will manage the share.
- In File Station, open the share and create a subfolder just for this app. Use your share name and actual volume number to build the NAS path. You can also check a local folder’s Properties → General → Location in File Station. For example, if the share is
dockeron volume 2 and your subfolder isreader, the path is/volume2/docker/reader. - Check that the subfolder exists and keep the path with your configuration. If you have an existing installation and cannot find its data, locate the old folder before starting with an empty one.
Use the Storage Manager walkthrough to trace a volume back to its storage pool and drives. A share may contain several applications. Separate their folders so permission changes or backups can target one app at a time.
Check which folder the container uses
In a bind mount, the NAS path comes before the container path. A mapping such as /volume2/docker/reader:/data makes the NAS folder available inside the container at /data. Use the internal path documented by your app.
Open Container Manager → Container, select the affected container and open Details → Settings → Volume Settings. Compare the mapping there with the intended folder in File Station. For a Compose project, check the corresponding volumes entry in the recipe before changing anything. The Container Manager project guide shows how to inspect the recipe and container logs.
Synology’s Node-RED example shows the NAS folder on the left, the container path in the middle and the mount mode on the right. Huncode cropped the original and underlined the mode.
| Symptom | First check |
|---|---|
| The NAS path does not exist | Verify the volume number, share and subfolder. |
| The app can read its files but cannot save | Check whether the mount is read-only, then check the NAS folder permissions. |
| File Station can open the folder but the app cannot | Verify which account or user ID the image runs as. Your DSM login can have different access. |
| A share or folder rule was just changed | Check the effective permissions and inherited rules before adding another entry. |
Inspect permissions on the dedicated app folder
In File Station, open the folder's Properties → Permission. Use Advanced options → Permission Inspector to check the effective access of a DSM user or group. The inspector is useful when an inherited entry and an explicit entry look different. If the image uses a numeric user ID, check its documentation before assuming that ID matches a DSM account.
If the image uses a known DSM account, grant that account only the access the app requires. In the permission editor, check which user or group the rule applies to and whether it covers the folder, its children or both. Keep any change within the dedicated app folder. Ask the NAS administrator to resolve unfamiliar denial rules or an unknown container identity.
A read/write mount allows writes through Docker. DSM still controls whether the process can write to the NAS path. Changing the mount mode will not fix an access rule on the folder.
Verify the change
Rerun the same action that failed. For an app that should write data, create a harmless test item, confirm it is stored in the intended folder, then check it again after a restart. For a read-only mount, verify that the intended sample opens. If access still fails, preserve the exact error and the mount settings before trying another permission change.
Upload and verify a file
Open the destination folder in File Station and choose Upload, or drag a file from your computer into the open folder. If the filename already exists, keep a separate copy before choosing to overwrite it. Download or reopen the file from that same folder and confirm it contains the expected content.
Documentation and image credit
The DSM workflow is based on Synology’s shared folder help, File Station permission controls, ACL inspector guide and container mount troubleshooting. The screenshot is from that last guide and is used with permission.