Lion, Apple's latest update to Mac OS X, has modest improvements in many areas, but few marquee features for veteran users. Jeff Carlson detailed those (Personal Technology, July 23), and explained how certain Lion additions might appeal to new users or those who never quite got the hang of Mac OS X.

However, there's a significant change that will affect any user who ever needs to deal with a Mac that won't boot because of corruption or a failed hard drive.

Lion radically revamps the recovery process for Mac OS X. In the past, Apple shipped with every Mac a CD or DVD from which that machine could boot; later it added USB drives into that mix.

After starting up from the disc, you could opt to select Disk Utility to repair a faulty partition, reinstall the operating system or perform a clean installation, or use Migration Assistant to copy a Time Machine backup onto the drive.

Lion has no installation DVD that ships with new Macs, and initially can be obtained only by purchasing it for $29.99 from the Mac App Store under Snow Leopard. The 4 GB Lion Installer downloads and, when run, uses some neat tricks to reboot and install without needing physical media.

In August, Apple will sell the installer for $69 on a USB drive, a nifty premium for something it clearly would rather not provide.

Apple's replacement for the disc is a separate partition on the startup hard drive. Disk partitions are a way to divvy up a physical hard drive into several seemingly independent looking volumes on the desktop, much like using cubicle walls to partition an office.

Recovery HD, Apple's term for this component of the system, creates a separate 650 MB partition that's invisible while you're using Lion, but available at boot time. While that seems like quite a bit of storage, it's not bad for an insurance policy, and a minuscule slice of a 500 GB or larger drive.

This partition acts like the DVD used to if you encounter trouble with the operating system, a faulty drive, or corruption in your boot partition.

Right after selecting Restart from the Apple menu, hold down Command-R, and your Mac, with Lion installed, boots into this mode. Apple offers four ways to proceed, three of which match the DVD boot options noted earlier: repairing with Disk Utility, reinstalling, and pulling in a Time Machine backup to replace the drive. The fourth is Get Help Online, which lets you read help documents in the recovery partition.

While in this mode, if you connect to the Internet via Ethernet or a Wi-Fi network selector, you can also access any website.

You might see a logical problem with reinstalling. If Apple requires a download to grab the 4 GB Lion Installer, where does that come from?

As long as the computer has an Internet connection, Apple can download the Lion Installer by sending your computer's serial number to the App Store (you can opt against this). Because you can install Lion on any number of machines at the same $29.99 price, it's unclear whether Apple sends the serial number as a warning ("We're watching you") or to check records.

Apple added an even niftier recovery mode if your hard drive is truly hosed and you need to either wipe it entirely or replace it with a new drive.

All Mac models released starting the day Lion shipped — the Air and Mini so far — will include Lion Internet Recovery, allowing them to boot over the Internet using files on Apple servers.

Obviously, an active (and fast) Internet connection is needed. The machine downloads the Recovery HD information, then proceeds as if it were booting off that partition.

The problem arises where a reinstallation is required and you're on a slow broadband or dial-up connection, or have metered or capped bandwidth.

Four GB isn't a lot for a cable modem or fiber network, or some faster DSL networks, but it's a many-hour download for a 1 Mbps DSL service, and impossible over dial up.

There are two perfectly good alternatives to Recovery HD and Lion Internet Recovery. The first is to delve into the special package that is Lion Installer and extract an embedded disk image you can burn to a DVD or write to a USB drive that allows you to boot an installation just like the old days. Macworld magazine has a blow-by-blow description at http://www.macworld.com/article/161069/2011/07/make_a_bootable_lion_installer.html

The other option is a bit simpler: purchase an inexpensive USB-powered external hard drive and install Lion onto it, then copy the Lion Installer on to that drive.

In Snow Leopard, after downloading and before installing Lion, you can find the installer in the Applications folder. However, after installing Lion, Apple oddly deletes the 4 GB file. You can download it again from the Mac App Store at no additional charge, however.

This may sound more complicated, but you'll never be at a loss for a missing installation DVD again, and you have many more options for getting back to a usable system than with any previous Mac OS X release

Glenn Fleishman writes the Practical Mac column for Personal Technology and about technology in general for The Seattle Times and other publications. Send questions to gfleishman@seattletimes.com. More columns at www.seattletimes.com/ columnists