Strange issue with permissions in docker (I think?)

[mchamp00]

qBittorrent version and Operating System

v4.3.4.1 running in docker v20.10.5 on Ubuntu server 20.04 LTS

If on linux, libtorrent-rasterbar and Qt version

QT v5.12.8
Libtorrent v1.2.13.0

What is the problem

Getting a "Cannot write to directory" error when trying to change the save path of a torrent in the list via right click -> "Set location."

What is the expected behavior

qBittorrent changes download location to desired location, moves the file.

Steps to reproduce

1. Download torrent to download location
2. Once complete, right click and choose "Set location"
3. Type the path of the mounted folder

Extra info(if any)

Directories in question are any top level mounted folder from either of my Synology NAS devices (DS918+, DS216j, both running the latest version of DS manager). Folders have been mounted via fstab and the owner/group ID are 1000 with permissions set to 775 for the main directory and all subdirectories and files. NFS permissions on the Synology are set to Dockerhost IP, permissions: read/write, squash: no mapping. I can navigate/read/write the mounted folders through the ubuntu shell with no issues. qBittorrent is running in docker image binhex/arch-qbittorrentvpn (though also reproducible with linuxserver/qbittorrent image) with PUID/PGID 1000, umask 002, defined volumes for mounted folders (as /movies, /tv, or /music). There is no problem when I try to download to any of these folders from the add torrent dialogue box on the UI, or when a torrent is auto-downloaded via a watch folder. Also, I can move the torrent to a subfolder within the top level folder without issue (e.g. /movies/moviename or /tv/showname). When I view the folders through the container shell, I see permissions as 775 with owner "nobody" and group "users." qBittorrent container log file is unremarkable.

I'm confused as to why I am able to read/write without problems from the Ubuntu shell and certain parts of the qBittorrent webUI, but can't change the directory to the top level mounted directory via "Set location." This isn't a breaking issue because I can work around it. I feel like this used to work, but I could be wrong. With the interactions of Ubuntu, docker, qBittorrent, and Synology, I've probably messed something up somewhere.

[FranciscoPombal]

Converted to discussion because usage with docker is not officially supported. Here, other users may help you getting your setup working. If you do uncover an actual bug in the troubleshooting process, please submit a new issue report (one may be created for you also).