Synnefo » Ganeti Instance Image

instances without the need for external tools such as debootstrap.

There are three types that are supported for deploying images.

  * tarball

  * qemu image

  * dump

To create a new qemu based disk image, you will need to able the ``CDINSTALL``

install medium::

  gnt-instance start -H cdrom_image_path=path/to/iso/ubuntu-9.10.iso, \

the amount of disk space used::

Note: Older versions of qemu-img may not support the ``host_device`` format so

use ``raw`` instead which should work in theory.

Dump

~~~~

The last, and most efficient type of disk image is creating filesystem dumps

using the dump command. The advantage with using dumps is that its much faster

to deploy using it, and it also has built-in compression. The disadvantage is

that you need to install grub manually which might be an issue on some operating

systems. We currently support grub 1, but anything using grub 2 will have issues

that I haven't found a solution for yet.

You will need to create images for both the boot and root partition (if you

include a boot partition).

Create a base image for an instance just like its described in Qemu Images. Make

sure the instance is shutdown and then issue the following commands (assuming

the activated disk is drbd1)::

  dump -0 -q -z9 -f ${IMAGE_DIR}/${IMAGE_NAME}-${ARCH}-boot.dump \

    /dev/mapper/drbdq-1

  dump -0 -q -z9 -f ${IMAGE_DIR}/${IMAGE_NAME}-${ARCH}-root.dump \

    /dev/mapper/drbdq-3

With swap::

Without swap::

NOTE: If you have kernel_path set, /boot will not be created and all partition

numbers will go up by one. For example:

With swap::

 /dev/$disk1    swap

 /dev/$disk2    /

Without swap::

 /dev/$disk1    /

dump:       $IMAGE_NAME-$ARCH-boot.dump

            $IMAGE_NAME-$ARCH-root.dump

Useful Scripts

~~~~~~~~~~~~~~

There are a set of useful scripts located in /usr/share/ganeti/os/image/tools

that you are welcome to use. These scripts are all intended to be run on the

master node::

  mount-disks $instance_name

  umount-disks $instance_name

This will mount or umount an instance to /tmp/${instance_name}_root

  ``make-dump $instance_name [ $IMAGE_DIR ]``

Create dump images for the given OS variant. You can override the default

$IMAGE_DIR setting by giving it as a second argument.

  ``make-qemu-img $instance_name [ $IMAGE_DIR ]``

Create an qemu image for the given OS variant.

IMAGE_TYPE: type of image being used (tarball, qemu, dump)

Included Custom Scripts

-----------------------

This OS definition includes three optional customization scripts that are

disabled by default. They are not required but are useful.

Grub

~~~~

When enabled, this can setup two things:

- Install grub into the MBR

- Setup serial access to grub

In general, the MBR will only be installed if you're not using a qemu image

type, or the ``kernel_path`` parameter is empty or initiating an import.  There

is currently no support for install a grub2 MBR (which Ubuntu Karmic requires).

Its recommended that you only use the qemu image type for Ubuntu Karmic until we

fix this.

If ``serial_console`` is ``True`` then this script will try to enable serial

support for grub.

Interfaces

~~~~~~~~~~

When enabled, it would try to setup networking for eth0 and enable DHCP. It

assumes you already have a DHCP client installed on the guest OS. This currently

supports the following operating systems:

- Redhat (CentOS/Fedora)

- Debian/Ubuntu

- Gentoo

- OpenSUSE

SSH

~~~

When enabled, it will clear out any generated ssh keys that the image may have

so that each instance have *unique* host keys. Currently its disabled for

Debian/Ubuntu since the keys won't be regenerated via the init script. We plan

to fix this manually at some point in the future.