How to install Xen-Tools on Ubuntu Server LTS 16.04 with Xenserver 7?

You first need to find out the physical path to the DVD drive by running:

sudo lsblk -f

The output can look like this:

NAME                 FSTYPE      LABEL           UUID                                   MOUNTPOINT
sr0                  iso9660     XenServer Tools 2017-02-14-21-45-52-00
xvda
├─xvda1              ext2                        b874af3a-24ec-454f-a802-0fee2945e388   /boot
├─xvda2
└─xvda5              LVM2_member                 LOmK2X-RYRD-GR8s-Guzv-kXFN-e3Y8-gSVdgM
  ├─nginx--vg-root   ext4                        2dd0c496-ea05-4027-bf90-84ceb94d2f3a   /
  └─nginx--vg-swap_1 swap                        77064139-1d50-4344-ade7-dacec1e62c9b   [SWAP]

As you can see, I already "inserted" the Xen Tools disk and the drive has /dev/sr0 physical path. Then, you need to create a directory where the drive will be mounted and then mount it:

$ sudo mkdir /mnt/dvd
$ sudo mount /dev/sr0 /mnt/dvd
mount: /dev/sr0 is write-protected, mounting read-only

Then, run the installer

cd /mnt/dvd/Linux
sudo ./install.sh

You can currently install version 6.2 (Which works with XenServer 7.2) with apt:

sudo apt-get install xe-guest-utilities

Though, as this will then get upgraded (either via apt-get updgrade or unattended-upgrades), it may become unstable when a new version of XenServer is released, so it may be good to pin it to version 6.* (/etc/apt/preferences.d/xe-guest-utilities):

Package: xe-guest-utilities
Pin: version 6.*
Pin-Priority: 900