Create directory to store VM images and set ACLs to allow libvirt-qemu to access:

mkdir -p /home/q/downloads/temp/vm
setfacl -m u:libvirt-qemu:x /home/q
virsh pool-define-as --name vm --type dir --target /home/q/downloads/temp/vm

Set the new directory as a libvirt storage pool:

virsh pool-define-as --name vm --type dir --target /home/q/downloads/temp/vm

Create new volumes for root and swaps:

virsh vol-create-as --prealloc-metadata --format qcow2 --capacity 8G --pool vm --name vm-name.root.qcow2
virsh vol-create-as --prealloc-metadata --format qcow2 --capacity 1G --pool vm --name vm-name.swap.qcow2

Create the VM:

virt-install --connect qemu:///system --os-variant debianwheezy --virt-type kvm --name vm-name --disk vol=vm/vm-name.root.qcow2 --disk vol=vm/vm-name.swap.qcow2 --ram 512 --cdrom /home/q/downloads/temp/iso/debian-jessie-DI-rc1-amd64-netinst.iso --graphics vnc --network bridge=virtbr0