seaweedfs: "mountpoint is not empty", but it is empty

docker-compose

  mount:
    image: chrislusf/seaweedfs
    volumes:
      - type: bind
        source: /mnt/weed
        target: /data
        bind:
          propagation: shared
    cap_add: ['sys_admin']
    devices: ['/dev/fuse:/dev/fuse']
    security_opt: ['apparmor:unconfined']
    depends_on: ['filer']
    # entrypoint: ls -a /data
    command: mount -filer=10.131.1.1:8888 -dir=/data -filer.path=/
    network_mode: service:tinc

produces

mount_1    | This is SeaweedFS version 30GB 2.26 ca74f64 linux amd64
mount_1    | mount point owner uid=0 gid=0 mode=drwxr-xr-x
mount_1    | current uid=0 gid=0
mount_1    | I0218 21:12:17     1 leveldb_store.go:40] filer store dir: /tmp/76f972a5/meta
mount_1    | I0218 21:12:17     1 file_util.go:23] Folder /tmp/76f972a5/meta Permission: -rwxr-xr-x
mount_1    | 2021/02/18 21:12:17 mount helper error: fusermount: mountpoint is not empty
mount_1    | 2021/02/18 21:12:17 mount helper error: fusermount: if you are sure this is safe, use the 'nonempty' mount option
mount_1    | I0218 21:12:17     1 mount_std.go:204] mount: fusermount: exit status 1
weed_mount_1 exited with code 0

but uncommenting entrypoint shows

mount_1    | .
mount_1    | ..
weed_mount_1 exited with code 0

so it is empty.

Setting it to a directory that doesn’t exist (for example /data/test) shows the standard help message (like weed help mount would.

A similar docker setup worked for moosefs:

  client:
    image: moosefs/client
    volumes:
      - type: bind
        source: /mnt/moose
        target: /mnt/moosefs
        bind:
          propagation: shared
    cap_add: ['sys_admin']
    devices: ['/dev/fuse:/dev/fuse']
    security_opt: ['apparmor:unconfined']
    depends_on: ['master']
    network_mode: service:tinc