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Images

A disk image is a file containing the complete contents and structure of an operating system; it is launched on a physical server to create your instance.  AppNexus provides base CentOS and Windows disk images available in the images directory on the public network attached storage share.  See Available Operating Systems. You can also create and launch any Linux-based distribution such as domUs, Ubuntu, Debian, etc.  See How to Create Custom Images for more information.  Please contact support at https://portal.appnexus.com/ or by e-mail (support@appnexus.com) if you wish to run a non-Linux-based OS.

The format of an AppNexus image is a gzipped tar archive (also known as a tarball) with the extension .tgz or .tar.gz.  Here is an example on Linux of how to convert an .iso file to a valid AppNexus format.

mkdir /mnt/debian
mount -o loop debian_64.iso /mnt/debian
cd /mnt/debian
tar cvzf /tmp/debian.fs.tgz .

You can reach base CentOS and Windows images from the public share folder, which has been mounted on your management instance by AppNexus Support. Here is a truncated manage-instance launch command example:

manage-instance launch --share-name=public --path=images/centos5-base/centos-current.fs.tgz . . .

Your own images can be stored in and reached from your private share folder.

Further Reading

Kernels

AppNexus uses a Linux-based kernel that is Xen-aware, which means it knows it is running as a virtual machine and will reduce any performance-degrading effects of virtualization.  For this reason a kernel inherent in your Linux-based disk image will be replaced with the AppNexus-compiled kernel.  Once your instance is running, you can make modifications to the kernel by installing your own custom kernel modules.

Please also note that there are a number of Xen-specific kernel modules that allow you to run applications like Samba client, IPFilter/IPTables, etc. in a virtualized environment.  These modules can be found as an RPM package at the location below.  We strongly recommend you install this RPM on your custom images so that you will be able to use all the features of your instances:

http://yum.local.appnexus.net/amd64/centos5/appnexus/RPMS/kernel-xen-2.6.18-128.7.1.el5.x86_64.rpm

If you wish to use a kernel other than the default kernel in your instance, please see Available and Custom Kernels.

As always, please create a ticket at https://portal.appnexus.com/ or contact us at support@appnexus.com if you have any questions or concerns.

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