I've recently been working on putting together a distribution based on OpenSolaris, OpenIndiana, and Illumos.
Called Tribblix, it was quite challenging to put together. I'll cover the individual pieces in more detail as time goes on, and put the code up so anybody else can do the same. But here's the rough overview of the process.
First, I've created SVR4 packages - I can do this either from an installed system, or from an on-disk repo. The IPS manifests contain all the information required to construct a package in other formats, not only what files are in the package, but also the scripting metadata that can be used to generate the SVR4 installation scripts. The most complex piece is actually generating the somewhat arcane and meaningless SVR4 package name from the equally arcane and meaningless IPS package name, making sure it fits into the 32 character limit imposed by the SVR4 tools. This has to be repeatable, as I use the same transformation in dependencies.
(An aside on dependencies: there are significant areas of brokenness in the IPS package dependencies on OpenIndiana, not to mention problems with how files are split into packages. There's significant refactoring required to restore sanity.)
Then I simply install the required packages for a minimal system into a build area. Of course, it took a little experimentation to work out what packages are necessary. There's an extra package for the OpenSolaris live CD that goes on as well.
There's then some fiddling with the installed image, setting up an initial SMF repository, SMF profiles, and grub. Something in need of more attention is the construction of the boot archive. I've got it to work, but it's not perfect.
The zlib archives you find on the live cd are then put together (these are lofi compressed iso images), plus an extra archive containing extra packages, and then mkisofs creates the iso.
The installer is very simple. I need to work on automating disk partitioning, as it's currently left to the user to configure the disk by hand. Then a ZFS pool is created and mounted up. The booted image is fairly minimalist, so that is simply copied across wholesale. It's unlikely that you would want less on the installed system than you would on the initial boot. I delete the live cd package, and then optionally add sets of additional packages.
Then grub configuration, setting up SMF for a real boot (which has different SMF profiles), creating the real boot archive (which currently takes an order of magnitude longer than it should), and finally setting up the live filesystems so they end up in the right place.
That's pretty much it. Descriptions of each step will be forthcoming in future blog posts, together with the code on github.