QEMU for Advance Users

As with comparable virtualization solutions, the guest and host can establish reciprocal network connections. But, of course, this also works between guests, assuming you are running multiple instances. All you need to do to accomplish this is to configure the virtual network card with the -net nic option:

qemu-system-x86_64 first_instance.img -net nic

The info network command lets you retrieve information about the instance's VLANs and the matching devices, as in the following example:

(qemu) info network
VLAN 0 devices: user.0: net=10.0.2.0, restricted=ne1000.0: model=e1000,mac-addr=44:55:00:12:34:56

QEMU has an integrated DHCP server, which supports automatic network configuration of the guest systems on the user mode network stack. For example, all network-capable guest operating systems can establish an external connection immediately after provisioning. If you enable the -net nic -net user options, this gives you an internal DHCP server (10.0.2.2) and a DNS server (10.0.2.3) on the internal network (10.0.2.0).

Another special feature of QEMU 2 is its support for live migration, which involves transferring running virtual machines from one host system to another. The QEMU developers recommend using an identical hardware configuration on the source and target systems.

A live migration comprises three steps. First, you need to execute the source instance on the source host. Second, you start a new instance on the target host using the same parameters. The important thing to remember here is to use the -incoming tcp:ip:port option. Third, you need to run the migrate -d tcp:ip:port command in QEMU Monitor on the source host.

Conclusions

QEMU 2 gives users an excellent virtualization environment that does justice to even the strictest requirements for stability and flexibility. The program impresses in particular in performance, with another bonus in the comprehensive documentation on the project website.