There are several pre-built images for OpenStack available from various sources. You can download such images and use them to get familiar with OpenStack. You can refer to http://docs.openstack.org/trunk/openstack-compute/admin/content/starting-images.html for details on using such images.
For any production deployment, you may like to have the ability to bundle custom images, with a custom set of applications or configuration. This chapter will guide you through the process of creating Linux images of Debian and Redhat based distributions from scratch. We have also covered an approach to bundling Windows images.
There are some minor differences in the way you would bundle a Linux image, based on the distribution. Ubuntu makes it very easy by providing cloud-init package, which can be used to take care of the instance configuration at the time of launch. cloud-init handles importing ssh keys for password-less login, setting hostname etc. The instance acquires the instance specific configuration from Nova-compute by connecting to a meta data interface running on 169.254.169.254.
While creating the image of a distro that does not have cloud-init or an equivalent package, you may need to take care of importing the keys etc. by running a set of commands at boot time from rc.local.
The process used for Ubuntu and Fedora is largely the same with a few minor differences, which are explained below.
In both cases, the documentation below assumes that you have a working KVM installation to use for creating the images. We are using the machine called ‘client1′ as explained in the chapter on “Installation and Configuration” for this purpose.
The approach explained below will give you disk images that represent a disk without any partitions. Nova-compute can resize such disks ( including resizing the file system) based on the instance type chosen at the time of launching the instance. These images cannot have ‘bootable’ flag and hence it is mandatory to have associated kernel and ramdisk images. These kernel and ramdisk images need to be used by nova-compute at the time of launching the instance.
However, we have also added a small section towards the end of the chapter about creating bootable images with multiple partitions that can be used by nova to launch an instance without the need for kernel and ramdisk images. The caveat is that while nova-compute can re-size such disks at the time of launching the instance, the file system size is not altered and hence, for all practical purposes, such disks are not re-sizable.
Copy the kernel and the initrd image from /mnt/boot to user home directory. These will be used later for creating and uploading a complete virtual image to OpenStack.
sudo cp /mnt/boot/vmlinuz-2.6.38-7-server /home/localadmin sudo cp /mnt/boot/initrd.img-2.6.38-7-server /home/localadmin
Unmount the Loop partition
sudo umount /mnt
Change the filesystem label of serverfinal.img to ‘uec-rootfs’
sudo tune2fs -L uec-rootfs serverfinal.img
Now, we have all the components of the image ready to be uploaded to OpenStack imaging server.
The last step would be to upload the images to OpenStack Image Service. The files that need to be uploaded for the above sample setup of Ubuntu are: vmlinuz-2.6.38-7-server, initrd.img-2.6.38-7-server, serverfinal.img
Run the following command
uec-publish-image -t image --kernel-file vmlinuz-2.6.38-7-server --ramdisk-file initrd.img-2.6.38-7-server amd64 serverfinal.img bucket1
For Fedora, the process will be similar. Make sure that you use the right kernel and initrd files extracted above.
The uec-publish-image command returns the prompt back immediately. However, the upload process takes some time and the images will be usable only after the process is complete. You can keep checking the status using the command nova image-list as mentioned below.
You can register bootable disk images without associating kernel and ramdisk images. When you do not want the flexibility of using the same disk image with different kernel/ramdisk images, you can go for bootable disk images. This greatly simplifies the process of bundling and registering the images. However, the caveats mentioned in the introduction to this chapter apply. Please note that the instructions below use server.img and you can skip all the cumbersome steps related to extracting the single ext4 partition.
glance image-create --name="My Server" --is-public=true --container-format=ovf --disk-format=raw < server.img
The status of the images that have been uploaded can be viewed by using nova image-list command. The output should like this:
nova image-list
+----+---------------------------------------------+--------+ | ID | Name | Status | +----+---------------------------------------------+--------+ | 6 | ttylinux-uec-amd64-12.1_2.6.35-22_1-vmlinuz | ACTIVE | | 7 | ttylinux-uec-amd64-12.1_2.6.35-22_1-initrd | ACTIVE | | 8 | ttylinux-uec-amd64-12.1_2.6.35-22_1.img | ACTIVE | +----+---------------------------------------------+--------+
