November 2011

To start off we are assuming you have an instance running on EC2 which you can ssh into. Here you can see a Fedora 15 instance running a mediawiki install. (click to see bigger screenshots)

The machine I was orchestrating the migration from was my local F15 laptop. I setup environment variables in my bash profile corresponding to the following:

• $EC2_USERNAME: my ec2 access key, retrieved from the AWS security credentials screen
• $EC2_PASSWORD: my ec2 secret access key, also retrieved from the AWS security credentials screen
• $RACKSPACE_USERNAME: my rackspace login name
• $RACKSPACE_PASSWORD: my rackspace API key, retrieved by logging into rackspace and navigating to Your Account > API Access

On my local laptop, I installed the deltacloud drivers for ec2 and rackspace. Deltacloud implements a client/server architecture for remote management, so I also installed the deltacloud client

$ sudo yum install deltacloud-core-ec2 deltacloud-core-rackspace rubygem-deltacloud-client

I then started deltacloud servers for both the ec2 and rackspace drivers (note it is now possible w/ the upstream deltacloud project to use the same server for multiple drivers)

$ deltacloudd -i ec2 -p 3002

$ deltacloudd -i rackspace -p 3003

Next I used the deltacloud client to retrieve information about my running EC2 instance

$ deltacloudc instances index -u http://$EC2_USERNAME:$EC2_PASSWORD@localhost:3002/api

Note in this screenshot, you can see the ec2 instance hostname which I can ssh to (due to the formatting of the field, 'amazonaws.com' has been truncated)

Now I ssh'd into the instance, specifying my keypair previously configured on Amazon when starting the instance

$ ssh -i ~/.ssh/mmorsi-keypair.pem ec2-user@ec2-107-22-56-233.compute-1.amazon.com

On the cloud instance, I used yum to install Snap. Until the Snap package is accepted and avaiable in Fedora / Ubuntu / other mainstream distributions, I have hosted binary packages in my own yum and apt repositories

$ sudo wget http://yum.morsi.org/repos/15/morsi.repo -O /etc/yum.repos.d/morsi.repo

$ sudo yum install snap

Due to how Amazon handles its cloud security policy (eg through their security groups concept), iptables is not setup on EC2 instances. Snap will by default backup and restore iptables rules, so we have to edit the snap configuration file to remove this backup target

$ sudo vim /etc/snap.conf

Remove the hightlighted content

Before running the snapshot, lets take a look at the options Snap presents us. Note Snap provides both a command line tool and a graphical GTK based one (more on snap coming in a future blogpost)

$ snaptool --help

Now we run the actual snapshot

$ sudo snaptool --backup --log-level verbose --norepos --packages --nofiles --services

This produces a snapshot in /tmp/snap-shot.tgz (the location of this can be configured by specifying --snapfile to snaptool). Back on our host system, we scp that file locally

$ scp -i ~/.ssh/mmorsi-keypair.pem ec2-user@ec2-107-22-56-233.compute-1.amazon.com:/tmp/snap-shot.tgz .

We can easily inspect the snapshot as it is a tarball (snap also supports snapshot encryption/decryption, protecting the contents of the tarball)

$ tar tzvf snap-shot.tgz

Next we goto launch a new instance on our destination cloud, Rackspace. To do this we first view the images available to base our instance off of

$ deltacloudc images index -u http://$RACKSPACE_USERNAME:$RACKSPACE_PASSWORD@localhost:3003/api

We've highlighted an image matching the OS out our source instance (note it is theoretically possible to restore the snapshot on a completely different OS! I have yet to try this out yet though so no guarantees)

Now we spin up a new instance using the selected image as the basis

$ deltacloudc instances create -u http://$RACKSPACE_USERNAME:$RACKSPACE_PASSWORD@localhost:3003/api --image-id 78

We see the ip address of the instance, which we can SSH to, right from this output. Once the instance is started (usually within a minute from my findings) Rackspace sends an email containing the root password

Before logging in, we scp our snapshot over to the new instance

$ scp snap-shot.tgz root@50.57.173.148:~/

We now ssh into the new instance

$ ssh root@50.57.173.148

We use the same wget and yum commands as above to install Snap

# wget http://yum.morsi.org/repos/15/morsi.repo -O /etc/yum.repos.d/morsi.repo

# yum install snap

Now we restore the snapshot, again using snaptool

# snaptool --restore -l verbose --snapfile snap-shot.tgz

Finally since the EC2 security groups mechanism is different than the standard iptables solution, and we weren't able to simply backup/restore the firewall policy (as Snap does by default), we need to open port 80 for http in our firewall. We use the text based firewall manager that ships w/ RH based system to do so

# system-config-firewall-tui

Bring up a web browser, point it at our new instance and WHALA! the world's first open source cross-cloud migration!