add gns3 repository

sudo add-apt-repository ppa:gns3/ppa

update apt

sudo apt-get update

install gns3 server

sudo apt-get install gns3-server

install kvm support

sudo apt-get install qemu-kvm libvirt-bin virtinst bridge-utils cpu-checker

make sure your system supports virtualisation

kvm-ok

than you should get something like this

INFO: /dev/kvm exists
KVM acceleration can be used

then run server

gns3server --host 192.168.7.15