The backup shell script copies a Mac OS X HFS+ boot volume to a target directory, including resource forks and Unix access rights. After downloading the file, open a Terminal window and go to the folder where you have stored the script (e. g. by typing "cd ", then dragging the download folder from the Finder to the Terminal window, then typing the return key). Then make the script executable by typing "chmod +x backup", followed by the return key. (The optimal place to store the backup script is the directory /usr/local/sbin. On Unix systems, there are local system binaries located.) Now assume a HFS+ backup disk or partition called BackupDisk. When mounted on Mac OS X, in the file system this volume is found at /Volumes/BackupDisk. To create a backup on this disk, type "sudo backup /Volumes/BackupDisk" in the Terminal window.
When the backup command has finished, it is possible to boot Mac OS 9 and Mac OS X from BackupDisk. Before starting the backup, verify that "privileges" are honored on the BackupDisk. Otherwise all files of the backup are owned by the currently logged in user, and the backup becomes worthless. To check the privileges settings, open the Info window for the BackupDisk in the Finder and switch to the Privileges pane. Then uncheck the "Ignore privileges on this volume" checkbox. (With the command line, you can check or modify this settings with the vsdbutil command. "sudo vsdbutil -c /Volumes/BackupDisk" shows the current privilege settings, "sudo vsdbutil -a /Volumes/BackupDisk" lets the system honor the privileges on the disk and "sudo vsdbutil -d /Volumes/BackupDisk" makes the system ignoring the privileges.)