My reason for using LVM is that I reinstall, upgrade and generally mess around with my OS installs so much that I have found that LVM gives me fantastic flexibility in moving, expanding, cloning and backing up my OS partitions at my leasure without the risks assosiated with other partitioning methods. It does, however, make multibooting your OSes a little complicated and unpredictable at times, especially on newer hardware, where the process gains another level of complexity.
What I'm talking about are the new UEFI (as opposed to BIOS) motherboards, which allow you use the full potential of, and to boot from, 3TB+ hard drives (when formatted in GPT as opposed to MBR). Things can get incredibly complicated and messed up because each time that you install a new OS on your machine, it will overwrite the EFI bootloader (.efi) files of your previous install and you will end up with a series of broken entries in your EFI "BIOS" bootlist and a load of pretty much redundant grub bootloaders scattered about your partitions. This offends me on so many levels, not least of which aesthetically.
NOTE: This was the OP's answer. I moved it down here as CW so it didn't get closed. If a mod sees this, please reparent ownership to the OP as a self-answer.
Below, I will detail how to get this all to work somewhat harmoniously and to sort the mess out, to some extent.
Part One: Installing.
Please note that if you are going to have Windows 7 (or 8?) installed on your machine, you'll probably have to install it first, preferably on it's own hard drive, and you won't be able to put it in your logical volume group. This is because the Windows 7 GPT/EFI installer is very basic and won't let you do the sorts of things you'll be doing here. After the windows install, you can resize and repartition, adding the partitions you need for a multi-boot install. The EFI system partition which Windows creates can always be re-used for the Linux installs, using a variation of the method detailed below.
Firstly, it helps to wipe your intended system drive using gparted (or the like) and initialise it as a GPT disk, before doing anything else. If you're a bit nervous about using a non-graphical partitioner to set up your disk from scratch, then this is definitely worthwhile and is easly done from a standard live Desktop USB or CD installer. Don't do it in Windows. I'm not sure that this is absolutely necessary, but it's what I did. You can also carry out the basic partitioning for the non-LVM partitions at this stage too, as it wouldn't hurt and gives you a framework for the installation proper.
Now burn your installation CDs/USBs. If you are using the Ubuntu Alternate Desktop ISO (recommended), then you must burn this onto a CD, as it simply will not work off of a USB stick. When used for an LVM install, it stops with a critical error when it tries to start loading and installing software with aptitude/tasksel, so use a CD if you know what's good for you!
Ubuntu Server installs absolutely fine from a USB in all cases (AFAIK), but I find that if I want to build an Ubuntu/Mythbuntu desktop system on top of Server, it introduces all sorts of unintended quirks which then need time spent sorting out. So stick with Desktop, if that's what you're after.
Quantal (12.10) has LVM as an option in the graphical installer (which is great!) and so the Alternate ISO has been done away with. However, I found the manual partitioning interface inflexible, lacking in LVM options, and simply did not work for multi-boot. This may have been due to the USB problem mentioned earlier, but to be honest, I had so many problems with a Quantal system I tried, that I gave up pretty quickly and went back to Precise (12.04.1).
The other main option is to use the Net-boot installer, which I don't have any real experience of (except on my Raspberry Pi), but I believe that there are mini ISOs with text-based and GUI (GTK) installers, which can be burnt and booted from. These pull most of the installation files directly from a repository and are highly customisable.
Next, you should boot up your system from CD or USB using it's UEFI boot entry from within "BIOS" or the boot menu (usually one of [F8] - [F12] on the keyboard).
I'll leave it up to you to get through preliminaries of the installation process, but once you get to the partitioning part, choose Manual Partitioning and then create (or modify if you have already created some of them) these partitions:
A single partition of size 200MB, FAT32, EFI System Partition, named/labelled "EFI", Boot-able, Format.
Several partitions: Sized 256MB, EXT2, Boot-able, Format;
You should name/label them each for the OS they will represent, i.e. "OS_01_Boot"..."OS_03_Boot"...etc.
Start by mounting the first of these as "/boot" and all the others as "do not use".
Create one partition for each OS that you intend to install.
One partition, taking up the rest of the space of the drive, as a volume for LVM.
Create one logical volume the same size as the physical RAM in your system i.e. 8GB, name it "Swap", use as swap, format.
Create one logical volume for each of the OSes within the volume group, sizing them as suggested above and giving them each a name i.e. "Ubuntu_12.04" etc.
Format each to EXT4, naming/labelling the partitions as you go.
Start by mounting the first of these as "/" (root) and all the others as "do not use".
That's it! Now you've got a swap, "/boot" and "/" (root) partition for your system and spares for your subsequent installations. You can now commit the changes to the partition table and continue with the rest of the installation.
When it comes to installing your next OS, just make sure that you mount the next "/boot" and "/" (root) partition, respectively. Please make sure that you mark all the others as "do not use", including the ones that you used last time.
Part Two: Backing up UEFI boot files.
As soon as you have booted into your new OS, you must backup your UEFI boot-loader for later use and to make sure that it is not overwritten in the next install. This can be found in "/boot/efi/EFI", within its own folder, usually named "ubuntu". The file in question will have a name similar to "grubx64.efi", depending on the architecture of your PC; so "/boot/efi/EFI/ubuntu/grubx64.efi", for my machine.
In my case, to back it up I copied it via the console, like so:
It would definitely be worthwhile making a further copy in your home folder or somewhere else safe, just in case:
Once this is done, you can safely install your next operating system (following the advice above), which will most likely overwrite the original file and folder and also make itself the default UEFI boot entry in "BIOS". Repeat the process again and as many times as is necessary, giving each folder a different, but representative name:
Part Three: Modifying the UEFI entries in your UEFI "BIOS".
From the terminal, enter:
You should get some output like this:
It's pretty self-explanatory, really. It should mirror what you see in your BIOS boot list.
Have a read of:
to see what the commands do, then modify the example commands below in order to add and remove boot entries.
First, remove that "Boot0000* ubuntu" line with:
Then we'll add some entries for three operating systems.
To change the boot order:
There's some pretty strange syntax involved, especially around the file paths, but it's pretty straightforward if you have a good guide (which I hope this is).
Thanks for reading. :)