Ubuntu 16.04 usb device automount

Mirchel

Hello,
I need to make something like live drive on SD card to load software on UpCore board + HighSpeed Carrier shield.
I used Yokto's boot system and kernel but as rootfs i used ubuntu base(core) 16.04 as i don't need any GUI and other apps that exists in Yokto, same time i need ability to install/remove applications on rootfs on SD card.
I use additional USB hub with USB SSD as datastorage to keep some data. Filesystem of that SSD is NTFS. The problem is that something - i suspect one of the instances systemd makes mounting of this SSD impossible.
When i try to mount this drive i get error - device or resource busy.
Let suppose that USB SSD is /dev/sdb, ok, i disconnect ssd and connect back to hub.
If nothing trys to get access to device i should have node for SSD as /dev/sdb, but new node is /dev/sdc!
So now i can freely mount SSD using ntfs-3g.
So question is - could someone suggest which service of systemd trys to automount USB SSD during boot?
How to disable automount of USB devices. I googled for that problem, but there is no real and working answer.
Thanks,