I think this problem might just be a general docker caveat and not a portainer oddity even.
When you use a bind volume, it will have some existing permissions, this will result in the user (9999:9999) who is running Baserow in the docker containers not being able to read/write to that bind volume.
Our docs should have a clearer section explaining:
- Troubleshooting steps with file system access
- Point out this problem explicitly with bind mounts and the solution (change its perms and owner manually to 9999:9999)
I’ve made an issue to track this change here: Add file system issues troubleshooting section to documentation (#1456) · Issues · Bram Wiepjes / baserow · GitLab