Adding to your comments for laptop users…

I would recommend for all users that for significant downloads like security updates or OS X updates it is also a good idea to use SW Update to only download — and not install — the update (or any others that require a restart). This allows the user to perform installations at a more convenient time and is a hedge against power failure or loss of Internet connection. To do this, first select the update(s) you wish to download, then choose Download Only from the Update menu.

This is also handy if updating multiple machines (from the same updater when running similar hardware and software on each Mac). Another benefit comes if you wish to reinstall later, you don’t have to download it again as it’s already on your hard drive.

To head off most System problems before they occur, I have found it is always best to ignore Software Update for System Updates. It makes for a good “heads up” that the Update is available, but it really is NOT the best way to update your System. The best method for a clean System is as follows:

- Go to Apple Downloads ( http://www.apple.com/support/downloads/ ), where you will usually have a choice between (for example) “Mac OSX 10.5.2 Update,” or “Mac OSX 10.5.2 *Combo* Update”. Choose the Combo Update even though it’s very much bigger, and takes longer to download. It contains everything new that was ever added to the original System version -in this example, 10.5.0, and reinstalls it in a shiny new, uncorrupted, pristine condition.

- Open Disk Utility and Repair Permissions on the hard drive targeted for Updating. You should also do this for anything you are installing that affects the System, including Security Updates.

- Open the downloaded Disk Image of the System Updater and drag the Installer to your Desktop, then run the installer from there.

- You will be asked to Restart, so do it.

- As soon as your Mac reboots fully, but before you do anything else, open Disk Utility and Repair Permissions on the hard drive you just updated. Again, you should do this also after any other installed System-affecting software.

- At this point, most folks will drag the Installer from the Desktop to the Trash. I say, save it somewhere, and I will tell you why. If things start to get really glitchy at a System level, you can just follow the steps above, reinstall this Combination Update and nine times out of ten, your problems will go away. I also save the latest Security, QuickTime, Airport, etc. Updates for the same reason.

My 2¢

I agree wholeheartedly with Jack on the combo updates. In my experience incremental (or delta) updates generally work fine, say from 10.5.1 to 10.5.2, but combo ones seem to be more reliable at keeping your system running smoothly. That is, users apparently report fewer problems after using them. If/when problems have been reported with system updates, you can pretty much bet that reports on the Mac web will reveal rerunning the installation with the combo updaters has cured many issues. Combo updaters can also be useful if updating multiple machines with different flavors of Leopard (or Tiger or whatever). For example, one 10.4.11 combo update would enable you to update machines whether they are 10.4.0, 10.4.1, 10.4.2 … up to 10.4.10. Just be mindful of your hardware (PPC updates will not work on Intel; for that you would need the Universal equivalent).

I would respectfully disagree re: repairing permissions. While permissions repair can be helpful, it would be also be safe to wait until after any software installation. It doesn’t hurt to repair before and after, but it is also redundant. Dan Frakes at MacWorld wrote an excellent article about repairing permissions in OS X in August 2006, and the lessons still apply. I’ve since followed his advice and have not experienced any problems. You can check out the article here: http://www.macworld.com/article/52220/2006/08/repairpermissions.html

@Jack and @Eric, thanks for the posts, good data. I want to elaborate a bit.

My opinion on why people report better luck with the combo updates is that they are already in a state of problems. Re-applying the update, which is only possible with the combo update, fixes things, thereby giving the impression of it being a better method.

I tend to be a little more nuts and bolts, and want to know why one would work better than the other. Don’t get me wrong, I am not challenging your methods, by all means, whatever works best is absolutely the best method to go with.

I have a feeling the reason that some have issues with the auto software update method is something interferes with the update, and it does not fully install. The OS thinks it installed, so you never get a chance to install again if there are issues.

@Eric, thanks so much for the link to the repair permissions dance, I knew it would come up, and I am in agreement with you. Strongly. I am not at all saying you are going to hurt anything, but it is a dance I feel people are very religious about, with no technical merit to it.

Apple has a doc on the matter.

When you use Disk Utility to verify or repair disk permissions, it reviews each of the .bom files in /Library/Receipts/ and compares its list to the actual permissions on each file listed. If the permissions differ, Disk Utility reports the difference (and corrects them if you use the Repair feature).

So, the real issue here is sure, first, it is only fixing permissions on files. Second, we should not blindly just fix them, we should want to know what changed them in the first place. A file will never just magically have wrong permissions applied to it. Knowing what is causing the permissions change is a better plan than blindly fixing something that is going to continue to break over and over again.

Apple even changed the way repair permissions works, as it was harmful in the past when people ran it too often.

Anyone really interested in the “voodoo” that is behind repairing permissions, and why it is really not this panacea, should read these, they are very good, and technically sound articles:
http://daringfireball.net/2006/04/repair_permissions
http://daringfireball.net/2004/12/software_update
http://daringfireball.net/2006/04/repair_permissions_voodoo

If one downloads the combo updater, and looks at it’s inner file contents, you will see, it is more or less nothing more than the single updaters Apple is shoving out in the automatic Software Update tool. So, one for one, it is doing the same thing. Combo updates just give you a chance to do it again. And yes, I am being very simple for the sake of keeping this post somewhat relevant, so do not beat me up to bad on what really is inside the combo update package files

Thank you both for your comments, both are relevant, and neither method will cause you harm, but I did want to back up the data with some technical info so people are not blindly following advice. Example, I have never used a combo updater, and I never have had a problem with my system, and my system is pretty heavily hacked.

Thanks so much again to both of you for contributing.

This is my first time using OSX Help. It is written very clearly. I am very glad I checked you out. I will be using your helpful information.
I greatly appreciate this and look forward to other
OSX tutorials. E.

Scott- My iMAC is only 3 weeks out of the box and unfortunatley,I am also on dial-up so downloading anything, including software updates is problematic.
I have set my updates file to ;manual; for obvious reasons. My computer says it is running 10.5.2 but an update check says I need about 270Mb of updates, including security,Safari,etc.
I have temporary access to a hi-speed connection (at a friends home).Question: should I have my friend download the latest Combo 10.5.2 download onto a thumb drive–or do I need to drag my entire computer to his home (50Kms distant) and just download the items as reported by my computer? The combo update and the individual updates are suspiciously similar in file size. I am assuming here that the apple download site will not recognize my friends P.C. in order to download the individual items as reported by my computer. Thanx–J.P.

@jp, you bring up a great point, which is not everyone can even run these updates due to slow internet speeds. If you had a laptop, moving it around would not be so bad.

In your case, let me explain as best as I can how Apple’s downloadable updates work.

When you run Software Update, or even a downloaded Combo Updater, or Single Updater, it will install what is called a BOM, or Bill Of Materials. This is like a packing list, and is stored on your computer. In a simple form, it lists what Apple updates have been installed in the past.

The next time you run an installer, the first thing it does, is look at your computer, and use its internal BOM to compare to the previously installed receipts for other updates.

It will then install only what you need, or it may re-install on top. You do not entirely know. What you do know, is Apple does make it near foolproof to run software updates. If you need it, it will let it, if it is not harmful, it will let it, if you do not need it, or it is harmful, it will not be allowed.

So yes, feel free to download the combo updater and run it. As far as I know, you should even be able to do this on your friends PC, and the combo updater will work just fine.

Now what about software updates? Where does the .dmg files go once they are installed?

The reason for the questions is I want to save all the updates to the OS and apps so that if I need to install them on another Mac I don’t have to waste time downloading again.

I use Speed Download which has some advantages over the software update app.

@Mark, in general, once you have installed a software update, you can delete it. In this day of super fast downloads, a replacement is not far away.

If you have a slower download connection, you may want to save the dmg files. I would just pick a nice place to archive them on your drive.