Debian 9

Open System > Administration > Synaptic Package Manager and search for linux-image

Mark the latest rt image and header for install then click on Apply.

linux-headers-4.9.0-19-rt-amd64
linux-image-4.9.0-19-rt-amd64

Reboot the computer and open a terminal Applications > System Tools > MATE Terminal and check that the rt kernel is loaded.

uname -a
Debian 9 Uname

You can now uninstall the non-rt kernels in Synaptic Package Manager.

Install Gdebi with this command

sudo apt install gdebi

LinuxCNC 2.7

Download the latest linuxcnc-uspace_2.7 deb at this time it’s 2.7.15 Uspace

Also downlowd the latest 2.7 documents deb 2.7.15 Documents

Also downlowd the latest 2.7 development deb 2.7.15 Development

In the file manager right click on each deb and install with Gdebi

LinuxCNC 2.8

Download the latest linuxcnc-uspace_2.8 deb at this time it’s 2.8.2 Uspace

Also downlowd the latest 2.8 documents deb 2.8.2 Documents

Also downlowd the latest 2.8 development deb 2.8.2 Development