andreas@nsn7:~$ time lxc launch ubuntu:yakkety
Creating good-mustang
Starting good-mustang

real	0m2.672s
user	0m0.016s
sys	0m0.008s

andreas@nsn7:~$ lxc exec good-mustang -- /bin/bash
root@good-mustang:~# sudo -u ubuntu -i
To run a command as administrator (user "root"), use "sudo <command>".
See "man sudo_root" for details.

ubuntu@good-mustang:~$