Utility of the week: AppleJack

Through references in passing in a forum discussion about OS X software updates, I found out about a tiny but very useful open source utility called AppleJack. Running the utility installs a new command "applejack", which is hidden from normal system usage but available when booted in single user mode (i.e., with Command-S pressed down). [Most of the time, if your system is so messed up that you cannot boot graphically in OS X anymore, you will still be able to do single-user boot. You get a BSD-only text prompt, which makes Unix sysadmins go "aha!" and regular Mac users panic. "applejack" allows you to "jack up" your Mac and fix a "pantsher" [flat tire] without calling a garage mechanic :-)]

What it does is provide a simple text-based menu for a number of troubleshooting utilities which are part of OS X. Holding COMMAND-S down while booting, you will now see a line suggesting that you run "applejack". When you type "applejack" at the command prompt you will get the following options:

[1] Repair disks                                                                
[2] Repair permissions                                                          
[3] cleanup cache files                                                         
[4] validate preference files                                                   
[5] remove swap files                                                           
[6] reboot                                                                      
[a] autopilot: steps 1-5 in sequence
[q] no thanks!

Steps [1] and [2] are basically the corresponding steps in "Disk Tools". [3]--[5] can be quite useful in getting a wedged or unstable system unstuck. [6] speaks for itself.

Note for sysadmins and other fellow geeks: the CMD-S have to be pressed on a keyboard DIRECTLY connected to the Mac. It won't work through a USB KVM switch (as I found out today ;-))