I use a Mac and I have come across something called 'disk permissions'. What is this?
Samantha, Mid-Levels
DQ: Disk permissions are intimately connected to software packages installed in a computer, including the most important of all: the operating system. Packages on the Mac end in .pkg and each time one is installed a 'Bill of Materials' file is put in the Library/Receipts folder. These files, which end in .bom, contain lists of all the files needed to install a package and the permissions needed for each file.
When Disk Utility is used to repair your machine's disk drive, it opens the .bom files and looks to see if the permissions are all correct. (Launching Disk Utility and telling it to check permissions will show you just how often these things need fixing.) Disk Utility will also repair them if you tell it to do so.
Most of the time you'd be better off simply leaving these files alone. If Disk Utility tells you that disk permissions need repairing, you should do it then leave it. Apple says you should not repair permissions if you have started your computer on a DVD-Rom or other disk. Always repair after starting the machine on your main hard disk. Also, make sure all updates have been downloaded and installed. For more information, see support.apple.com/kb/HT1452. I find Google's Gmail filing system, where all messages for each e-mail subject are stacked together, most annoying. Is there a way to reformat this, so I can remove unwanted correspondence and retain only relevant ones?
Mary Melville, Kowloon