I have created a new Linode, Rsync'ed all my stuff over and (hopefully) I have successfully duplicated my config on the new server. If I use the IP swap and it doesn't work as expected can I swap back or will it break my Linode??

An IP swap is little more than a reboot with a different IP address; if it can survive a reboot, it oughta survive an IP swap.

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One point of note if you have anything bound specifically to that address i.e. you're not using 0.0.0.0 or you have a static IP you'll want to update those configurations before you switch the IP.

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