I have a m1.large Debian based server on EU-West. Recently due to some changes in organization's policies we are to move to Rackspace. How would i move an AWS EC2 EU-West Debian Instance to Rackspace? Unfortunately it wasn't setup by me so i don't know exactly what and how it was configured, by a rough estimate i think i would need about a week to setup a fresh one with everything installed and configured same as this one.
I have also seen some scripts/posts that suggest to use same distro, same kernel on both source and target and then just rsync whole system(excluding few directories) to target.
Yep, an rsync could work, and I've been involved in plenty of migrations where this method was used. However given that you have no real knowledge of the existing system, this might be the right time to take on a project to rebuild the machine from scratch the right way (documented, automated, reproducible... all the good things).
Creating a new image from an existing one is always a problem especially if you need to reverse engineer it, and even worse when you need to migrate to another cloud. Consider using tools like https://github.com/devstructure/blueprint to help you with reverse engineering your image into Chef recipe. Having a chef recipe makes it easier to migrate between different cloud images.
Proper disclosure: I am a fulltime Cloudify developer. If you wish to avoid cloud vendor lock-in at the application level (and not just the image), you should consider Cloudify http://www.cloudifysource.org We run nightly Cloudify test suites on Rackspace, Amazon EC2 and HPCloud using standard images provided by each of the cloud providers. Each application installs and manages itself on a clean image using predefined recipes. These recipes could also be chef recipes.