[I submitted this hint to MacOS X Hints, but there won't be any updates today, so I decided to post it here as well.]

In OS X, I think it is odd that some applications demand that you reboot the system after installing, using the GUI installer.app in the Utilities folder. The beauty of the Mach Kernel is, that you can dynamically load device drivers, without reloading the kernel, but just by restarting the kext daemon (kextd).

I set out to try if I could install an application with the CLI-installer, that demanded reboot when installed with the GUI installer, without rebooting. And why not try with iChat AV?

I downloaded the installer, fired up terminal.app and typed:

% sudo installer -pkg ~/Desktop/iChatAVBeta.pkg -target / -verbose

At first, the installer ran, and was over in a little less than a minute I think. System optimization jumped from 30% to 100% in one line, which I found a bit strange. I looked in my /Applications folder, but iChat AV was nowhere to be found, and neither was the original iChat. Odd.

I ran the installer again, same command, same result. No iChat AV, no iChat. I then changed directory to the root-directory and ran the installer again:

% cd /

% sudo installer -pkg ~/Desktop/iChatAVBeta.pkg -target / -verbose

This time it behaved, and I could see the System Optimization bit taking a lot longer than my previous attempts. So far so good. Trying to start iChatAv yielded nothing but a spinning beacball - time to restart the kext daemon, which i did by grepping through top results, to find the PID of the daemon.

% top -l1 | grep -i kextd

This will return the PID of the kextd process, which I then send a kill -HUP command

% sudo kill -HUP

Now I should actually be able to start up iChatAv, and doing so loaded the app just fine, but never introduced a buddy list, or anything else. Clicking on the menu bar would return a spinning beachball for a short while, and then nothing.

So I quitted the app, restarted kextd a couple more times from the CLI, but to no avail - iChat still wouldn't start up.

I then logged out, and logged back in, which must have done something, because now I could start iChatAV.

It should be practically possible to install it without rebooting, and without logging out and then back in, but I don't know what went wrong in my case. But at least I didn't have to reboot (: