Memo

VyOS seemed to change release policy ago. LTS(Long Term Support) Release is provides to subscriber. Subscriber includes commercial customer and contributor. If you are not subscribed, subscribe or get rolling release builds.

Here is about upgrade v1.1.8 to v1.2.0(rolling release).

Open your console

Connect ssh or other way to VyOS.
Check to running image.

$ show system image

The system currently has the following image(s) installed:

   1: VyOS-1.1.8 (default boot) (running image)
   2: VyOS-1.1.7
   3: VyOS-1.1.6
   4: VyOS-1.1.5
   5: Old-non-image-installation

Download and add image

Download latest rolling release build or choose what you like.
VyOS Downloads

!Notice! If you are reboot soon will boot new image but sometimes occur problem.
At your own risk.

$ add system image https://downloads.vyos.io/rolling/current/amd64/vyos-rolling-latest.iso

Perhaps you answer yes to the questions you are asked. me too. :p
You can see added image when retype "show system image".

$ show system image

The system currently has the following image(s) installed:

   1: 1.2-rolling-201912030217- (default boot)
   2: VyOS-1.1.8 (running image)
   3: VyOS-1.1.7
   4: VyOS-1.1.6
   5: VyOS-1.1.5
   6: Old-non-image-installation

Reboot to apply new image

Let's reboot.

$ reboot
Proceed with reboot? (Yes/No) [No] Yes

Let's pray.

Few minutes later reconnect to VyOS. Check the Version.

$ show version
Version:          VyOS 1.2-rolling-201912030217
Built by:         autobuild@vyos.net
Built on:         Tue 03 Dec 2019 02:17 UTC
~~

That's done it.