Synology NAS DSM 6.1 with Active Directory (AD) installed on the NAS. Users in AD and Synology NAS users. On the NAS is SMB v1 disabled 

Connect from Ubuntu 16.04 LTS (Latest Stable Version) Gnome desktop 

from the terminal: 

as root:

sudo su -

mount -t cifs //<ip address or DNS name Synology NAS>/<Share> /mnt (or other mount point) -o username=<AD user or NAS user>,vers=<2.1 or 3.0> 

To start within Gnome GUI from terminal:

as root:

nautilus 

or as user: 

sudo mount -t cifs //<ip address or DNS name Synology NAS>/<Share> /mnt (or other mount point) -o username=<AD user or NAS user>,vers=<2.1 or 3.0> 

To start within Gnome GUI from terminal:

sudo nautilus

Connect from Centos 7

from the terminal: 

as root:

sudo su - or su - 

mount -t cifs //<ip address or DNS name Synology NAS>/share -o,user=<AD user or NAS user,domain=<AD netbios domain or other name for NAS users>,vers=<2.1 or 3.0> /mnt (or other mount point)

To start within Gnome GUI from terminal:

as root:

nautilus 

or as user: 

sudo mount -t cifs //<ip address or DNS name Synology NAS>/share -o,user=<AD user or NAS user,domain=<AD netbios domain or other name for NAS users>,vers=<2.1 or 3.0> /mnt (or other mount point)

To start within Gnome GUI from terminal:

sudo nautilus