Geklärt:
folgende Zeile war Schuld
/dev/disk/by-uuid/868A1CE88A1CD711 /mnt/868A1CE88A1CD711 auto nosuid,nodev,nofail,x-gvfs-show,ro 0 0
# /etc/fstab: static file system information.
#
# Use 'blkid' to print the universally unique identifier for a
# device; this may be used with UUID= as a more robust way to name devices
# that works even if disks are added and removed. See fstab(5).
#
# <file system> <mount point> <type> <options> <dump> <pass>
# / was on /dev/sdb1 during installation
UUID=7f0db80f-0658-4fc4-b617-305656201f28 / ext4 errors=remount-ro 0 1
# swap was on /dev/sdb5 during installation
UUID=b2f7843d-863e-440b-859d-c7cfa2d500cc none swap sw 0 0
/dev/disk/by-uuid/868A1CE88A1CD711 /mnt/868A1CE88A1CD711 auto nosuid,nodev,nofail,x-gvfs-show,ro 0 0
aus /etc/fstab entfernt bzw. deaktiviert..
Gruß