Request Permission to Update, Sir.

John Gruber over at Daring Fireball's been involved in an interesting exchange with various other people on proper procedure for software updates. He gives some very good advice all in all, and it's something that all Mac newbies and OS X converts should look at.

What's worth noting is his adressing of the now-classic troubleshooting technique, Repair Permissions:

I still stand behind my original advice, that Repair Permissions is something you should turn to as a troubleshooting tool, but many of you disagree. For those of you who report that Repair Permissions frequently turns up files with incorrect permissions, however, I suspect it’s a sign of some deeper problem with your Mac OS X installation. File permissions and ownership don’t have a half-life — they don’t rot or “go bad” or even change over time. If they’ve changed, some software had to have changed them.

Of course, the reason people tend to run Repair Permissions immediately after installing system and security updates is that installers are the software most likely to modify these file attributes. It’s anecdotal evidence at best, but for what it’s worth, I have two Macs on which I’ve never run Repair Permissions, which have been updated with every system and security update over the last two years, and which exhibit no permission/ownership-related problems whatsoever.

On both of my Macs and on my friend's Macs, Repair Permissions always reports some error with Permissions, even though I religiously try to keep my system as clean and tidy as possible, using Disk Utility and Disk Warrior to scan and check my disk. Often times it's something with the filesystem or Microsoft Word. I've also noticed after iCal, iSync, or QuickTime updates that some permissions do get changed, and are reported as such by Repair Permissions.

Now, what I don't know is if this is simply natural, just a byproduct of the installation process which isn't really indicative of any significant change to the system. Maybe it's just an artifact of the installer shuffling files around during the installation process. What I'd like to see is a UNIX guru step up to the plate and give some explanations to how the Permissions system in OS X works with respect to what we see in the Repair Permissions report window.

I'll totally agree with Gruber's assertion that Repair Permissions is needed only when you have problems that are strongly indicative of permissions-related issues. Beyond that, repairing your permissions is truly another perceived panacea on the level of rebuilding your desktop or zapping your PRAM in the old OS 9 days. Yes, these problems did happen, and they were an issue -- but they didn't happen often enough to cause the problems that people thought could be solved by using those measures. But I still personally think that a permissions repair after a system update would be good idea. And yes, I do agree that the actual empirical evidence for this is flat-out zero. Now if you'll excuse me, I have some sugar pills to take for my headache.

Anyway, next:

However, a vocal minority of users swear by the use of combo updaters. The idea being that there are occasional problems caused by the delta updaters, which problems can be avoided by using combo updaters. After every system update, sites such as MacFixIt and MacInTouch publish reports from readers claiming that update problems were fixed after running the combo updater.

However, I don’t think it’s necessary. I use Software Update for all the machines in the house, and the delta updaters have never caused a problem. Again, I’m not arguing that the three active Macs here at Daring Fireball HQ constitute a statistically significant sample size, but my guess is that most of the people who run into problems with delta updaters have diddled with files they ought not have diddled.

Gruber then cites an example of one L337 Mac user on MacInTouch who fixed a graphical issue on a newly upgraded 10.3.7 system by using the ATi driver from his previous 10.3.6 installation. Now, I agree with Gruber. Unless you *really* know what you're doing, you should never, ever, ever mix and match system components. Back in OS 9, this wasn't so bad, since it usually involved an extension or control panel that you could easily toss out if it caused problems. But this is UNIX now -- files you may transfer from an old system aren't so easy to get rid of. It's easy to confuse files in the deep UNIX underpinnings of the system, and you may end up changing something else in the process, and the system may not let you delete it easily.

Now with respect to delta vs. combo updaters, the arguement to me is similar to the update vs. clean reinstall issue when dealing with major system updates (i.e. 10.x to 10.[x+1]). Since the delta updaters only give you only the extra files your system needs, the files you may not need for the update are still kept from the old installation. These files may have been corrupted or changed in some way, or even missing. Since the combo updater gives you fresh copies of those files too, any "wronged" files will have been replaced with clean ones.

Of course, this is based on my own limited understanding of the distinction between combo and delta updaters and yes, there isn't a lot of factual evidence to back this up. Maybe I'm totally off-base with this. But better safe than sorry, I think.

Another problem is that, from my own observations, the updater seems to base the composition of the delta updaters based on the current state of your system. Hence, the size and composition of a delta updater may change from system to system, depending on what updates you have and haven't installed. So the update itself may be quite variable. Isn't that what delta means?

When I decided to do a clean reinstall of Panther on my system after a botched security update, after painstakingly reapplying all of the updates up to 10.3.5, I applied the 10.3.6 delta updater. It didn't work. It said it couldn't be used on my computer, even though I'd made sure I installed everything system related up to that update. But then I got to thinking that I hadn't updated everything. There was still Safari, the various freeware iApps, and other Apple miscellany (like ADC developer stuff). Maybe those updates changed aspects of the system that Software Update had reported to Apple when I downloaded my delta updater. Since those changes weren't there, the installer had nothing to work with.

I bit the bullet and downloaded the combo updater, and lo and behold, everything worked out fine.

I don't by any stretch of the imagination think that my situation is indicative of any widespread problem with delta updates. But I think that it should give pause as to the reason why people prefer combo updaters over delta ones.