➜  ubuntu-box vagrant up                  
Bringing machine 'default' up with 'virtualbox' provider...
==> default: Importing base box 'ubuntu/xenial64'...
==> default: Matching MAC address for NAT networking...
==> default: Checking if box 'ubuntu/xenial64' version '20191024.0.0' is up to date...
==> default: A newer version of the box 'ubuntu/xenial64' for provider 'virtualbox' is
==> default: available! You currently have version '20191024.0.0'. The latest is version
==> default: '20191108.0.0'. Run `vagrant box update` to update.
==> default: Setting the name of the VM: ubuntu-box_default_1573432329297_29440
==> default: Clearing any previously set network interfaces...
==> default: Preparing network interfaces based on configuration...
    default: Adapter 1: nat
==> default: Forwarding ports...
    default: 22 (guest) => 2222 (host) (adapter 1)
==> default: Running 'pre-boot' VM customizations...
==> default: Booting VM...
==> default: Waiting for machine to boot. This may take a few minutes...
    default: SSH address: 127.0.0.1:2222
    default: SSH username: vagrant
    default: SSH auth method: private key
    default: Warning: Connection reset. Retrying...
    default: Warning: Remote connection disconnect. Retrying...
    default: 
    default: Vagrant insecure key detected. Vagrant will automatically replace
    default: this with a newly generated keypair for better security.
    default: 
    default: Inserting generated public key within guest...
    default: Removing insecure key from the guest if it's present...
    default: Key inserted! Disconnecting and reconnecting using new SSH key...
==> default: Machine booted and ready!
==> default: Checking for guest additions in VM...
    default: The guest additions on this VM do not match the installed version of
    default: VirtualBox! In most cases this is fine, but in rare cases it can
    default: prevent things such as shared folders from working properly. If you see
    default: shared folder errors, please make sure the guest additions within the
    default: virtual machine match the version of VirtualBox you have installed on
    default: your host and reload your VM.
    default: 
    default: Guest Additions Version: 5.1.38
    default: VirtualBox Version: 5.2
==> default: Mounting shared folders...
    default: /vagrant => /Users/sushiver/ubuntu-box

Now do vagrant ssh-config to login to the virtual machine.
$ vagrant ssh-config

Output:

➜  ubuntu-box vagrant ssh-config
Host default
  HostName 127.0.0.1
  User vagrant
  Port 2222
  UserKnownHostsFile /dev/null
  StrictHostKeyChecking no
  PasswordAuthentication no
  IdentityFile /Users/sushiver/ubuntu-box/.vagrant/machines/default/virtualbox/private_key
  IdentitiesOnly yes
  LogLevel FATAL

Important points for Windows Users:

Windows user should take a look at IdentityFile in above output. They must use private_key to connect to Virtual Machine using Putty tool.

Windows user will first convert private_key to public key using puttygen, and then use putty or WinSCP to connect to VM.

Windows user can also use vagrant ssh, but for that they need to install openssh-client on Windows machine.

Till now, you have setup Ubuntu virtual machine, and you are good to setup kops tool on it.