KVM-Manager

Authors: * Daniel Kahn Gillmor dkg@fifthhorseman.net * Jamie McClelland jm@mayfirst.org * Greg Lyle greg@stealthisemail.com

License: GPL-3+

This is a small set of scripts to make it relatively easy to manage a stable of kvm instances in a fairly secure and isolated fashion.

The basic model is to use runit to supervise each KVM instance, with a single, non-privileged user account for each instance. You can login via ssh as the non-privileged user and, via screen, access the instance's console.

Dependencies

runit : for system supervision
kvm : for the virtual machine emulator
socat : For communications with the monitor and console of guests
screen : for the detached, logged serial console
bridge-utils : for configuring a bridge device
lvm2 : for creating the relevant block devices
udev : for configuring the block devices with proper permissions
fakeroot : for rebuilding the initramfs as a regular user in di-maker
xorriso : for grub2 to make an iso in di-maker
genisoimage : for di-maker to work with an existing iso
sgabios : for early pre-bootloader (like ipxe) output

Recommendations +++++++++++++++

openssh-server : i've been using ssh to access the vm's serial console

INSTALLATION

Install dependencies:

apt-get install runit kvm screen bridge-utils lvm2 udev socat sgabios

If you want to be able to use di-maker, you'll also need:

apt-get install fakeroot xorriso grub2

Link programs into /usr/local/sbin:

ln -s $(pwd)/{di-maker,kvm-manager,kvm-creator} /usr/local/sbin/

Link screen configuration file into /etc

ln -s $(pwd)/screenrc.kvm-manager /etc/

Configure your host network to use a bridge. If your network adaptor is eth0, you can use the following in /etc/network/interfaces
```
auto br0
iface br0 inet static
  [Put your normal IP config for eth0 here...]
  hwaddress ether xx:yy:zz:aa:bb:cc
  bridge_ports eth0
```
Note: explicitly setting the hwaddress of your bridge to the same MAC address as your existing NIC ("ip link show eth0 | grep ether") is a good idea -- it seems to avoid periods of network connectivity outages for the host when new interfaces get added to or removed from the bridge.

Alternately, you can create an internal-only bridge, and tell your host to pass traffic to it:

auto br0
iface br0 inet static
  [ internal IP address information ]
post-up echo 1 > /proc/sys/net/ipv4/conf/br0/forwarding

INSTALLING DEBIAN ONTO YOUR VIRTUAL SERVER

To create a KVM instance, run:

kvm-creator create $GUESTNAME [ $VG [$DISKSIZE [$RAM] ] ]

You can replace "create" with "demo" to see the default values for non- specified options.

The creator scripts creates a username and home directory, logical volume, and the required directory in /etc/sv/kvm/GUESTNAME from which the kvm-manager script is run. After creating your virtual server, you can modify the files in /etc/sv/kvm/GUESTNAME/env to change initial settings.

You may also add ssh key's to /home/GUESTNAME/.ssh/authorized_keys to provide additional access to other users.

At this point, your virtual server is created, however, it has no operating system and it has not been started.

There are two options for installing debian onto the virtual server:

netboot
iso (like a CD install)

To use netboot, make sure you have a working DHCP server running on your host server and offering addresses over your bridge interface.

Then, indicate that the server should boot via the network with:

touch /home/$GUESTNAME/vms/$GUESTNAME/netboot

Alternatively, you can make a debian boot ISO image:

Make the directory /usr/local/share/ISOs
Create a serial console enabled debian installer.
cd /usr/local/share/ISOs
di-maker d-i.iso

Indicate that the server should boot via the CDROM (the equivelant of putting the installer CD in the drive) with:

ln -s /usr/local/share/ISOs/d-i.iso /home/$GUESTNAME/vms/$GUESTNAME/cd.iso

STARTING YOUR VIRTUAL SERVER

update-service --add /etc/sv/kvm/$GUESTNAME

This process adds your virtual server to the runit service directory.

If /home/$GUESTNAME/vms/$GUESTNAME/cd.iso exists, the server will behave as if you set the CDROM as the boot device in the bios.

If /home/$GUESTNAME/vms/$GUESTNAME/netboot exists, the server will behave as if you set the network device as the boot device in the bios.

After you have installed your server, be sure to delete these files if they exist or your server won't boot properly.

ACCESSING YOUR VIRTUAL SERVER

To access the guest's serial console, do:

ssh -t $GUESTNAME@host.machine screen -x $GUESTNAME

To access the guest's KVM monitor, do:

ssh -t $GUESTNAME@host.machine socat vms/$GUESTNAME/monitor.socket STDIO

HACKING

All patches, fixes, suggestions welcome!