"File exists" error on starting torrent download

[stephenboston]

What is the issue?

I have a VirtualBox setup for torrents like this:

Both host and guest are Arch linux on 6.8.6-arch1-1 kernel.

On the host, we have an external drive/dev/sdb mounted to /mnt/sdb, The mount is owned by transmission:transmission.

On the guest we have a sshfs mount of host:/mnt/sdb to guest:/mnt/sdb (Shared folders not working)
Permissions are identical on both sides and uid/gid for transmission are the same value.

On the guest, /var/lib/transmission/.config/tranmission-remote/settings.json sets the download directory to /mnt/sdb/transmission/downloads

I can add a magnet link through the web-ui. The torrent is started, metadata retrieved, but then we get the error :

 ERR open-files.cc:160 Couldn't create '/mnt/sdb/transmission/downloads': File exists (17) (open-files.cc:160)

transmission is started by root through a systemd service in /lib/systemd/system/transmssion.service

    [Unit]
    Description=Transmission BitTorrent Daemon
    Wants=network-online.target
    After=network-online.target
    
    [Service]
    User=transmission
    Type=notify
    ExecStart=/usr/bin/transmission-daemon -f --log-level=error
    ExecReload=/bin/kill -s HUP $MAINPID
    NoNewPrivileges=true
    MemoryDenyWriteExecute=true
    ProtectSystem=true
    PrivateTmp=true
    
    [Install]
    WantedBy=multi-user.target

Which application of Transmission?

transmission-remote

Which version of Transmission?

transmission-cli 4.0.5-1

[killemov]

The systemd service file doesn't look very interesting. Am I correct to assume your external drive does not have a partition table but a single flat partition? Can you manually write anything in that folder from your VirtualBox guest environment as user transmission? If no, then at least it is not a transmission problem.

[stephenboston]

Your assumption is correct.

I can create and delete files and directories in the /mnt/sdb/transmission directory where 'I' is stephen, a member of transmission group.

Something I forgot to say: the .config..torrents and .config..resume directories are symlinks to /mnt/sdb/transmission/torrents and /mnt/sdb/transmission/resume. I do this because I want to version the config but not the data. Problem?

[killemov]

I can create and delete files and directories in the /mnt/sdb/transmission directory where 'I' is stephen, a member of transmission group.

You really need to test this from your VirtualBox environment as user transmission. Create /mnt/sdb/transmission/downloads as transmission, chmod 777 it, and let transmission-daemon(?) run again.

.config..torrents and .config..resume don't mean anything to me.

Under Debian the two folders resume and torrents are located in /var/lib/transmission-daemon/.config/transmission-daemon which also seems weird but works.