My main linode for my website is running an older stack (LAMP, with older versions of PHP and MySQL, and Ubuntu 8.04).

I've gotten everything working (I think) on a new linode, under LEMP, with current PHP and MySQL, and Ubuntu 10.04 LTS).

After I migrate, if I wanted to keep the older system around, just in case I needed to boot it, what do I have to do?

I'm thinking: delete everything I know I won't ever need off the old image (logs, backup files, etc). Then shrink the ext3 filesystem on the control panel. Then buy a new linode, only buying as big as I need to mount that image. Copy the image over, and boot.

That should work: no software should change, the older kernel will stay there, everything (except the IP address) will be exactly the same, right?

Delete everything you don't need and shrink the image, then deploy a new image as the new OS. You don't need to create a new linode to do that, nor do you need a new linode to boot into the old image (just create a different configuration profile for that image).

To make it even more compact, you could store a compressed archive of the old filesystem, although you can't easily boot into that like you could a shrunken disk image.

The old kernel will not stay there if you deploy a new configuration profile. The kernel is not part of your disk image unless you use a custom kernel.

By the way, why deploy Ubuntu 10.04 now? You could wait another couple of months when the next LTS (12.04) comes out, set it up, and call it a day for the next 5 years. Packages in 10.04 are already out of date by almost 2 years.

N00b alert.... are you guys saying the same thing, or something different?

The current system is on a Linode 2048. I'm pretty sure I can shrink it down to the smallest available (since I don't care about RAM much if I'm only booting it 'once in a blue moon').

If I delete everything I don't need, resize my partition and resize the linode down to the lowest available, can I just leave it there 'forever', if I'm willing to eat the monthly fee. I don't want to change kernels, the whole point was to be able to spin up the box 'as it was' if I needed to look for something.

1. If the disk image is going to stay on the same linode and you don't touch any configuration profiles, yes, the kernel will remain the same for as long as Linode is willing to support it.

2. If you copy the disk image over to a new linode (as Guspaz suggeted), you will have to set up a new configuration profile with the exact same parameters as before. This is not difficult at all, you just need to remember to do it.

But honestly, very few things on a typical LAMP/LEMP stack depend on kernel versions, so it shouldn't matter either way. You should be using the 3.0 kernel if you're on any recent Linux distribution.

Anyway, did you use spawn-fcgi or php5-fpm for the new LEMP stack? If spawn-fcgi, you're all set. If php5-fpm, be very careful, because most third-party FPM packages for Ubuntu 10.04 are horribly outdated (and therefore insecure). Just another sign that 10.04 is on its way out.

It's running php-cgi, so I assume that's a flavor of spawn-fcgi?

php_info.php shows:

Server API CGI/FastCGI

Since he's looking to keep the linode just as a 512 instead of a 2048, he doesn't need to copy the image, he can just resize the disk, then resize the linode.