Here's a primer on partitioning a Mac

Here's a primer on partitioning a Mac


It's possible to run a whole bunch of different operating systems on a PowerPC Macintosh if the hard drive is big enough.

Different operating systems can peacefully coexist on a properly partitioned Mac hard drive.
Some OSes are easier to load than others, of course. The key is partitioning the big drive correctly ahead of time.

My test system, an Apple G4 Cube, came with a 40G hard drive and Mac OS 9. In anticipation of using multiple OSes, I first partitioned the drive into three sections with Apple's Drive Setup utility. When I booted from the system CD-ROM, Drive Setup displayed a simple graphical interface for specifying partition size and formats.

Partitioning a drive completely erases the contents, however, so I reinstalled Mac OS 9 on the main partition.

Not only did I want the advantages of running applications written for different OSes, I also knew that partitioning gives a degree of data protection. A catastrophe that requires reformatting of one partition can leave the others untouched.

Note, however, that if the physical disk fails, all partitions are likely to be lost at once. Partitioning doesn't free you from making system backups, which should be kept on a different disk altogether.

Besides the advantages already cited, partitioning is a way to limit the disk space available to certain operations. For example, Virtual PC 4.0 from Connectix Corp. of San Mateo, Calif., which many Mac users rely on for working with PC apps, creates a virtual drive that grows as needed, up to 10G. I prefer to keep it in its own partition where it can't hog that much room.

The basic Mac Hierarchical File System for storage has the greatest compatibility with non-Apple OSes. But HFS dates from the days when a 20M drive was considered large. On multigigabyte drives formatted with HFS, files can take up more room than they should because HFS can't handle the multiple divisions needed for maximum efficiency.

To resolve this, Apple issued the extended or HFS+ format. I chose a 30G HFS+ partition for my main OS and files. I then set aside two other partitions of about 4G each in the more compatible HFS format.

One was for Mac OS X, the other for Linux. I could have set the Linux partition in Apple's Unix format, known as A/UX. But because it would be a while before I installed Linux, I chose to keep it under HFS. That was a mistake.

How the 40G drive splits up four OSes

' First partition (30G under HFS+): Mac OS 9.0.4

' Second partition (4.3G under HFS): Mac OS X

' Third partition (3.3G under HFS): Virtual PC emulator

' Linux partitions (1G total): 50M under HFS/ boot for Linux startup; 840M A/UX /root for main Linux partition; 128M A/UX swap for Linux memory management

The Mac OS X beta went onto the second partition with no difficulty. Because OS X is itself a full-featured Unix environment, I did not really need Linux as well, but I wanted it.

Virtual PC 4.0 emulates in software a Pentium II MMX'not exactly Intel Corp.'s latest processor. Performance, however, depends on the Mac processor, and the 500-MHz G4 made it quite acceptable.

Virtual PC comes in versions for Microsoft Windows 9x, Windows 2000, PC DOS and Red Hat Linux. Version 4.0 includes a full, licensed copy of Win98; the other OSes are or will be available as plug-ins. I installed Virtual PC on the third partition and was running Windows applications from OS 9 in no time.

When it came to installing Linux, I knew that Apple's Drive Setup wouldn't let me convert the open HFS partition into three smaller parts with different formats, unless I wanted to erase the whole hard drive.

Other apps can reformat just one partition at a time. I intended to use Linux's own pdisk partitioning utility, but then I ran into a classic bootstrap issue.

LinuxPPC 2000 [GCN, May 15, 2000, Page 25] wouldn't boot on the G4 without some finicky system tweaks. The OS on the CD-ROM from LinuxPPC Inc. of Madison, Wis., couldn't be adjusted, of course, and I couldn't format the third partition to accept Linux without the pdisk utility, which I couldn't reach because I couldn't boot Linux.

Second is better

So I installed LinuxPPC's Mac-based launcher on the second partition instead, next to OS X. Booting from there, I could start the installer on the CD, from which I sliced the third partition into Linux-friendly pieces. At last I could install Linux.

In the end, I have four operating systems on the Cube, and only Linux is still giving me trouble.

To choose which OS to boot, I have three control panels. Startup Disk in OS 9 lets me select among OS 9 disks, including CDs. System Disk lets me choose OS 9 or OS X and is available from both systems. And LinuxPPC comes with BootX. If I change my mind while the machine is off, I can also hold down the Option key during startup to see a menu of Mac system disks.

Joel Sparks, a free-lance reviewer in Silver Spring, Md., has been a government lawyer and database programmer.

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