UPDATE: AutoDMG makes this process, "stupid easy" so I'm going to move away from the below to using that tool. Also, if you're master distribution point is a JDS you cannot compile configurations. Again AutoDMG to the rescue.

Ever since Casper Admin has allowed for compiling configurations way back in the 10.5/6 days I have been successfully creating an OS.dmg via Casper Admin. I still use this method today & since 10.7 this DMG also includes the Restore Partition.

The end result is an DMG of the OS that has never been booted & is an asr image. Much like DMG’s created by InstaDMG & AutoDMG.

I’m not sure why I seem to be the only one doing this, but below is the how;

NOTE: The below example is when using Casper Admin v9.x & the "Install Mac OS Mavericks.app." The steps will be similar when using one of the new OS's delivered via the App Store. If using an older OS the method will be a little different... But I've sadly forgotten those steps.
Also, the install app needs to support the Hardware/OS you'll be creating the OS.DMG on (so if the Build mac is on 10.9, then 10.8 will not install).
It is advised that you perform the below actions on a Mac that is located on the same VLAN as the JSS, due to speed as you'll be installing the OS to a DMG across the network.
Lastly, I've only ever performed the below using Mac OSX hosted JSS & DP's, with the CasperShare mounted via AFP.

1. On your chosen Build Mac, download Mavericks from the App Store.
2. Once downloaded, open Casper Admin v9.x & drag the “Install Mac OS Mavericks.app” into the packages pane. With Casper Admin v9.x will copy over just the InstallESD.dmg within the .app bundle. When using older version or Casper & maybe pre-Mavericks app bundles you may need to locate & copy the InstallESD.dmg from within the app bundle instead.
3. Once copied, located the uploaded InstallESD.dmg & double click it to bring up the Information window.
4. Once in the Information window, change the package priority to 1 & optionally rename the DMG. (I often rename the DMG something like: 001 10.9.2 InstallESD 260214.dmg. DO NOT tick requires restart.
5. Create a standard configuration in Casper Admin.
6. Next enter the Management account details, (these are required but the account is not created via this method).
7. Drag the previously upload DMG into the Configuration. (If wanted, you could add other packages.. but i’d advise to create a Vanilla Base OS.dmg & to add the other packages to a configuration later).
8. Once the DMG is in the Configuration, click the Compile button to the lower left of the Casper Admin window.
9. At the “Create a compressed disk image?” prompt, read the wording & select the most prudent option for your deployment method.
   
10. Casper Admin will prompt you to enter Administrator credentials twice during this process, & one more time per additional package you add. This can be avoided by running Casper Admin as root.
11. Casper Admin will now start compiling the configuration. This will create a DMG under /CasperShare/CompiliedConfigurations/<configuration name.dmg>
12. Once the compiling is completed, the image is then scanned for restore.
13. When the compiling is completed, you should be returned to the packages pane. With Casper Admin open, navigate to /CasperShare/CompiliedConfigurations/ & drag the compiled dmg into the packages folder. You can also rename the DMG if wanted at this stage too.
14. Quit Casper Admin & relaunch, the dmg should then appear in the packages pane as unknown.
15. Double click the dmg, & in the information window change the package priority to 1.
16. That’s it. The DMG is now ready to be used as your OS.dmg in your configurations as per your setup. For me, as you can see in the above screen shots, we have a 10.9 Base Standard Configuration & Smart Configurations under that. Whenever we create a new OS.dmg we replace the previous version with the newly created.

I hope someone else finds this useful. If you use the Casper Suite & only need an vanilla OS.dmg, i’d suggest giving this ago.

Of course, there is still nothing stopping you using InstaDMG & AutoDMG (& intact in a few situations they work better). But you can’t have too many options!

One oddity to mention, is that is you use this method & FSTAB. The Restore Partition still works, but is located as a after the OS partition & not the last partition on the disk as per the below;

This doesn’t affect the ability to use the Recovery Partition to boot into, nor does it affect the MDM lock or wipe functions. Also, Casper Imaging resizes the DMG when imaging as appropriate. But the Recovery Partition stays at 650MB.

However, I’ve not attempted FileVault2 with multiple partitions as I understand this will only encrypt the OS partition & as our Users data is on a second partition.. there is little point to me using it.