The following template can be used to install an Ubuntu 16.04 server with 4GB RAM, 2 virtual CPUs, 60GB hard drive, and bridged network interface.
sudo virt-install
--name YOUR-VM-NAME
--ram 4096
--disk path=~/kvm/images/YOUR-VM-NAME.qcow2,size=60
--vcpus 2
--os-type linux
--os-variant generic
--network bridge=br0
--graphics none
--console pty,target_type=serial
--location '/home/base3/ubuntu-16.04.3-server-amd64.iso'
--extra-args 'console=ttyS0,115200n8 serial'
You'll notice the storage format is qcow2. The reason for this is to allow snapshots of the VM to be taken with ease.