One can do a similar thing currently with a Time Machine backup on a Mac using a USB disk. One boots the Leopard installer and then connects the Time Machine disk; there is a restore menuchoice that allows you to choose the state to restore from.

My MacBook boots from an external USB drive without problems, so things seem to be in good order now.

I agree that I rarely need the install disk image, but it’s quite easy to make and I’m quite intolerant towards the wait that comes with booting from DVD.

Of course the thing I really am missing is the ability of the damn installer to simply install an OS on drive B while I’m using the machine from drive A. That was a basic feature of the installer back in the classic Mac OS days and it was much more convenient than the control freak install process we have these days.

Yes, I could have used an ordinary FireWire drive, but the iPod mini is so much more convenient, and I happened to have one around!

I don’t really feel the need to have a clone of my entire startup volume, primarily because it’s big (all these audio samples from GarageBand/Logic, etc.) and I feel that, if I ever get a problem that requires a complete reinstall, I am quite likely to want to start from scratch anyway. (This hasn’t happened in quite a while, even with my involvement in the AppleSeed program, which is a testament to the overall reliability of OS X. But of course I am always at the mercy of a hard drive failure.) I use SuperDuper! for nightly backups of my user folders, though (as well as other important partitions, of course).

The need for an external install volume is not as crucial for Leopard as far as I am concerned, since all the machines that can run Leopard come with a DVD drive (except for the MacBook Air, of course, but I have yet to encounter a client with one).

I suspect the Leopard image would fit on a dual-layer DVD. It just doesn’t fit on a single-layer DVD, which is the most common kind. But recent Macs can burn DL DVDs as well, so you should be able to put it on one of those.

Web-based stuff is still far into the future as far as I am concerned. Even with a decent high speed hookup (which I don’t have), downloading a multi-GB image would still be rather time-consuming, as opposed to booting/installing from a DVD. When I am on a house call, I need a readily available solution. But I suppose it will come eventually.

For PPC computers, fortunately, FireWire drives are still widely available. It’s just too bad they don’t make FW iPods anymore. But of course they have pretty valid reasons for switching to USB.

The image for Leopard is larger than one can burn onto a DVD using Disk Utility, so Apple did some tricks to get it to fit on the DVDs they shipped. Future Mac OS X images are certainly going to be smaller, at least at first, because the PowerPC architecture is going to be dropped.

I’ll wager that all future MacBooks are provided without inboard DVD drives and without firewire, so Apple will have to use some kind of web-based technique to distribute the OS. Perhaps they will provide access to an up-to-date image on their web server so that you can make a local copy on a flash RAM disk or, even better, so you can boot from it over the web. (Given the current trouble with MobileMe, however, I wonder if that can be reliably done given present levels of connectivity—I wouldn’t want to try that over a satellite link.)

For the present, ssp is right, though, the PowerPC users like myself are hosed for booting off USB media.

Things I’d note:

1. You’ll certainly run into problems with modern iPods and late PPC machines as far as booting from USB is concerned.

2. Of course you can use your steps for ordinary hard drives as well.

3. In fact, I consider it a good idea to simply always keep a hard drive copy of my installation disk around. It turns a slow startup and install process into a rather quick procedure. Of course using a drive that’s faster than an iPods may be even better for this.

4. I didn’t need to copy an installation disk over many times so far, so I always get the steps wrong. But I started suspecting that one can easily grab the image, pimp it and write it to disk with a few asr commands. Surely someone must have noted them and put them in a readymade script?