repair disk permisions??

In disk utility, what does repair disk permissions do and when should we do it? Does it maintain a healthy mac? Thanks.

It checks all the permissions (access types) of all your files and makes sure that none are broken or corrupt.

It is a good idea to run repair permissions after you install something new, or if you are having any weird behavour. I tend to run them whenever I am checking someone's computer just to be sure that all is in proper working order.

Doesn't hurt to do it, so feel free to run them whenever you feel like, say, once a week, if you get a lot of junk of the internerd.

Cool Jude...thanks..we had a machine die with an internal 1 tb seagate RAID and we can't get the data recovered (wierd) so I'm not taking any chances..

I believe that repairing permissions only works for the system drive. Not external drives or secondary drives. I might be wrong about that but I seem to remember seeing that somewhere.

As for maintaining a healthy mac, there are a bunch of janitorial programs out there that are either free or available for a small donation that are designed to run the periodic clean up programs on a mac. I've been using Onyx lately, but I've also used Cocktail and Mac Janitor. They perform functions that the OS only performs if you leave it on constantly.

I'd get one of those programs (downloadable from versiontracker.com) and clean up your mac every week or every 2 weeks or so.

Andy

As Andy mentioned these programs perform tasks that OS also performs if you leave your Mac on. So if possible, leave it on, which is what I do. If you can't do that, at least leave it on from Friday to Monday, as I've read somewhere that OS is set to perform these janitorial jobs on weekends.

Disk Utility should be run at least every two weeks, or every time you have a crash, install something new, or get weird behaviour. The best way to do it is shutting down the computer, turn it on in safe mode, run disk utility (select repair disk permissions after selecting the Name of your boot disk), and restart your computer.

The janitorial maintenance routines (mostly clearing caches) are usually set to run in the early am every day, but only if the machine is on and not sleeping. This time can be reprogrammed in the Terminal fairly easily, or you can use one of the programs mentioned to do it manually (I prefer Cocktail). Generally it's not a big deal if you only do it once a week.

As for disk repair, the First Aid feature of Disk Utility will not work if you are booted from your main drive; you can run Verify though and if it sees problems you then boot from the OSX DVD and run First Aid on your boot drive. Another way is to boot in single-user mode (apple-S) and follow the onscreen prompts to run the fsck routine which will also repair the disk. I use a free utility called Applejack which can be run in SU mode and which performs mutiple repairs and jobs in sequence (including the janitorial cache stuff).

Phil, it sounds like you're having a major problem with the data on your RAID that may go beyond these measures. I highly recommend you get a copy of Diskwarrior and run that on the RAID; it will hopefully help you recover your files and do a more thorough job of repairing the disk. Here's what I would do:
Repair Permissions, First Aid, Diskwarrior, repair permissions again.

More than you ever wanted to know:

'periodic daily' runs on your machine at 3:15 am, 'periodic weeky' runs at 4:30 am, and 'periodic monthly' runs at 5:30 am.

You can run any of these by hand by opening up an Applications, Utilities, Terminal and typing:

sudo periodic daily [enter]

...for example. The system will require you to put your password in--assuming you are an administrator.

All three work that way. Leave time if this hasn't been done in a while.

The book "Running Mac OSX Panther" (O'Reilly) suggests changing the timing so these tasks run automaticaly when the machine is more llikely to be on and awake. None of these will run while the machine is sleeping.

None of this is likely to help you. Having a major crash is cause to run some heavy rescue software like Diskwarrier or starting the machine from the System CD (or DVD) and running First Aid from there.

Koz