It is my understanding that a user boots from the startup CD (the install CD or DVD) in order to Repair Disk, not Repair Permissions. Repairing permissions can be done that way but it is not the best way. It is better to repair permissions while booted from the hard drive.
Jon
macOS 11.7.10, iMac Retina 5K 27-inch, late 2014, 3.5 GHz Intel Core i5, 1 TB fusion drive, 16 GB RAM, Epson SureColor P600, Photoshop CC, Lightroom CC, MS Office 365
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