Q:

VMbuilder hangs

I am trying to build a Ubuntu 14.04 image for kvm with vmbuilder but it hangs:
I am trying to build a Ubuntu 14.04 image with vmbuilder like this:
vmbuilder kvm ubuntu -o -v --suite trusty --arch amd64 --rootsize 9216 --user testuser --pass testpass --hostname test --addpkg libjson-perl --addpkg liburi-encode-perl --addpkg curl --addpkg acpid --addpkg openssh-server --addpkg memcached --addpkg php5-memcache --addpkg nfs-common --addpkg dmidecode --addpkg unzip --addpkg default-jdk --addpkg mysql-server  --addpkg libstring-shellquote-perl --tmpfs - --domain mydomain.com --ip 10.1.1.2"

And I get:
2016-04-15 16:58:57,769 INFO    : Mounting tmpfs under /tmp/tmpbH0ZdGtmpfs
2016-04-15 16:58:57,794 INFO    : Calling hook: preflight_check
2016-04-15 16:58:57,816 INFO    : Calling hook: set_defaults
2016-04-15 16:58:57,817 INFO    : Calling hook: bootstrap

The machine I am building on is running 12.04 LTS. If I substitute trusty for precise in the above command, it does not hang.
How do I fix this?

A:

The problem was that one can only build a 16.04 image on a 16.04 host with vmbuilder and I was using a 12.04 host.

