http://fedorapeople.org/groups/docs/release-notes/ja-JP/sect-Release_Notes-Changes_for_Sysadmin.html
PermitRootLogin without-password
vi /etc/ssh/sshd_config
====
PermitRootLogin without-password
====
If this option is set to “without-password”, password authentication is disabled for root.
systemctl restart sshd.service
qemu-0.15