add system image https://downloads.vyos.io/testing/1.2.0-rc1/vyos-1.2.0-rc1-amd64.iso
Trying to fetch ISO file from https://downloads.vyos.io/testing/1.2.0-rc1/vyos-1.2.0-rc1-amd64.iso
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  357M  100  357M    0     0  5025k      0  0:01:12  0:01:12 --:--:-- 2820k

ISO download succeeded.
Checking for digital signature file...
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   836  100   836    0     0    861      0 --:--:-- --:--:-- --:--:--   861
Found it.  Checking digital signature...

gpg: directory `/root/.gnupg' created
gpg: new configuration file `/root/.gnupg/gpg.conf' created
gpg: WARNING: options in `/root/.gnupg/gpg.conf' are not yet active during this run
gpg: keyring `/root/.gnupg/pubring.gpg' created
gpg: assuming signed data in `/var/tmp/install-image.12397/vyos-1.2.0-rc1-amd64.iso'
gpg: Signature made Mon 08 Oct 2018 12:59:16 PM CEST using RSA key ID A0FE6D7E


gpg: Can't check signature: public key not found
Signature check FAILED.


Do you want to continue anyway? (yes/no) [no] OK. Proceeding with installation anyway.
Checking MD5 checksums of files on the ISO image...OK.
Done!
What would you like to name this image? [1.2.0-rc1]: OK.  This image will be named: 1.2.0-rc1
Installing "1.2.0-rc1" image.
Copying new release files...
Would you like to save the current configuration
directory and config file? (Yes/No) [Yes]: Copying current configuration...
Would you like to save the SSH host keys from your
current configuration? (Yes/No) [Yes]: Copying SSH keys...
Running post-install script...
Setting up grub configuration...
Done.