Clone an Existing Instance

Problem

You have a running instance, perhaps with EBS volumes attached, and you want to make a clone of that instance.

Solution

Use the get_userdata and clone_instance functions in this recipe to create a copy of an existing instance, including copies of all attached EBS volumes based on the latest available snapshots.

Discussion

For this recipe, let’s assume that you have a running instance. It could have one or more EBS volumes attached to it. Let’s also assume that, for some reason, you want to create another instance that is an exact copy of the currently running instance. You may want to do this because the running instance appears to be having issues or it may be that you want to debug an issue without disturbing your production instance.

Whatever the reason may be, this recipe defines a function to help us clone a running instance. To accomplish this, we need to gather some information:

• We need to know the AMI, keypair, security groups, availability zone, instance type, etc. of the current instance. We can get all of that information easily from the boto Instance object that represents the current instance.

• We need to make copies of all EBS volumes that are attached to the instance. For this recipe, we will assume that the latest snapshot of the volumes represents the state we want to recreate.

• We need the user_data that was passed to the instance when it was started. This data could include data and/or scripts that are run when the instance is launched as shown in Executing Custom Scripts upon Instance Startup.

Example 2-11. Clone a Running Instance

import boto
from boto.ec2.blockdevicemapping import BlockDeviceMapping, BlockDeviceType
import os
import base64

def clone_instance(instance):
    """
    Make an clone of an existing Instance object.

    instance      The Instance object to clone.
    """
    new_bdm = None
    ec2 = instance.connection

    if instance.block_device_mapping:
        root_device_name = instance.get_attribute('rootDeviceName')['rootDeviceName']
        user_data = instance.get_attribute('userData')['userData']
        # user_data comes back base64 encoded.  Need to decode it so it
        # can get re-encoded by run_instance !
        user_data = base64.b64decode(user_data)
        new_bdm = BlockDeviceMapping()
        for dev in instance.block_device_mapping:
            # if this entry is about the root device, skip it
            if dev != root_device_name:
                bdt = instance.block_device_mapping[dev]
                if bdt.volume_id:
                    volume = ec2.get_all_volumes([bdt.volume_id])[0]
                    snaps = volume.snapshots()
                    if len(snaps) == 0:
                        print 'No snapshots available for %s' % volume.id
                    else:
                        # sort the list of snapshots, newest is at the end now
                        snaps.sort(key=lambda snap: snap.start_time)
                        latest_snap = snaps[-1]
                        new_bdt = BlockDeviceType()
                        new_bdt.snapshot_id = latest_snap.id
                        new_bdm[dev] = new_bdt
                    
    return ec2.run_instances(instance.image_id,
                             key_name=instance.key_name,
                             security_groups=[g.name for g in instance.groups],
                             user_data=user_data,
                             instance_type=instance.instance_type,
                             kernel_id=instance.kernel,
                             ramdisk_id=instance.ramdisk,
                             monitoring_enabled=instance.monitored,
                             placement=instance.placement,
                             block_device_map=new_bdm).instances[0]