While using the GNS3 network simulator, in certain labs it was needed to use special hosts, with provisioned and preconfigured software f.e. to test AAA with RADIUS or TACACS+, or to provide services like syslog or a webserver. These tasks are quite time consuming if virtual end devices are not at hand when you need them. Along with it they are even more time consuming if one does not the right tool at hand.

For a copy/paste installation a working terminal like xterm or urxvt is the tool. QEMU at default starts with VGA emulation, where mouse buffers might not work be working properly in X, if the right commands have not been used.

Starting a virtual host with QEMU a serial console and binding it the loopback interface , here TCP port 4321:

user@host % qemu-system-x86_64 -boot d -cdrom vyos-1.2.0-amd64.iso -hda vyos.qcow2 -enable-kvm -m 1G -serial telnet:localhost:4321,server,nowait

While the guest is starting run following command to verify the TCP ports:

root@host % ss -tuln | grep 4321
tcp    LISTEN     0      0      127.0.0.1:4321               0.0.0.0:*                  
tcp    LISTEN     0      0         [::1]:4321                  *:*   

Now connecting to to the guests serial console running on loopack device should be working:

user@host % telnet localhost 4321
Trying ::1...
Connected to localhost.
Escape character is '^]'.

Welcome to VyOS - vyos ttyS0

vyos login:

This method will also work by binding to the serial console to prefixes like f.e.: 0.0.0.0 and 192.0.2.1.