获取有关奇怪目录的信息

Question

Joplin桌面应用程序(https://joplin.cozic.net/)在/tmp中创建了一个目录，我无法以root用户的身份获得任何信息：

当以常规用户身份登录时，我可以输入dir，甚至不能显示其属性：

regularuser@homehost /tmp % ls -ld .mount_JoplinHNsadS
drwxrwxr-x 4 root root 0 Sep 30 21:48 .mount_JoplinHNsadS

regularuser@homehost /tmp % lsattr .mount_JoplinHNsadS
lsattr: Function not implemented While reading flags on .mount_JoplinHNsadS/AppRun
lsattr: Inappropriate ioctl for device While reading flags on .mount_JoplinHNsadS/app
lsattr: Function not implemented While reading flags on .mount_JoplinHNsadS/joplin.desktop
lsattr: Operation not supported While reading flags on .mount_JoplinHNsadS/joplin.png
lsattr: Inappropriate ioctl for device While reading flags on .mount_JoplinHNsadS/usr

但是，root甚至不能进入这个目录：

root@homehost /tmp % ls -al | grep mount
ls: cannot access '.mount_JoplinHNsadS': Permission denied
d?????????  ? ?    ?         ?            ? .mount_JoplinHNsadS

root@homehost /tmp % file .mount_JoplinHNsadS
.mount_JoplinHNsadS: cannot open `.mount_JoplinHNsadS' (Permission denied)

为什么会发生这种事？我以为root可以访问任何目录，即使设置了像/tmp这样的粘性位？

如何诊断这样一个目录为根？这个目录是如何创建的？

Answer 1

感谢迈克尔·汉普顿：

% mount | fgrep .mount
Joplin-1.0.111-x86_64.AppImage on /tmp/.mount_JoplinHNsadS type fuse.Joplin-1.0.111-x86_64.AppImage (ro,nosuid,nodev,relatime,user_id=1000,group_id=1000)