It is both inconvenient and less safe to keep backup volumes mounted when not in use. A mounted volume is more prone to corruption, and open file dialogs needlessly spin up mounted volumes, contributing to a user experience latency that is most apparent if the primary drive is solid state.

By creating an /etc/periodic/hourly directory modeled after the existing /etc/periodic/daily directory, and adapting com.apple.periodic-daily.plist, there is a place to put a script that handles mounting and unmounting the Time Machine backup disk, and launching Time Machine.

Another valuable free utility has gained Snow Leopard support, with the release of DasBoot 2.0.

This is a tool for making custom boot devices from a USB flash drive or other USB or FireWire media, including an iPod. It can import a variety of diagnostic utilities (Disk Warrior, Drive Genius, TechTool Pro and more) from their bootable install discs and configure them for use on the same device. You'll obviously need the appropriate license key to use commercial software.

It's also possible to update the installed software, so there is no need to burn a new disc every time one piece of software gets an update. This version of DasBoot works with 10.5 and up; there is also an older (1.0.3) version available for Tiger.

The only real limitation comes from the inability of PowerPC Macs to boot OS X from a USB drive. If you need to repair both Intel and PowerPC systems, a portable drive with a FireWire 400 (and possibly USB as well) interface is the way to go.

[crarko adds: I've used previous versions of this on both an 80 GB iPod and a small FireWire 400 drive, and it works great. Between this, AppleJack, and Winclone if you use BootCamp, it's easy to build a comprehensive repair and recovery suite. I've had to try to customize similar tools in the Windows world, and it's quite a bit more of a pain in the neck to accomplish.]

I had been experiencing extremely high CPU utilization by the DirectoryService process. Most of the time it was at 65% CPU usage, and sometimes it was up to 190%.

I traced this to my usage of the /etc/hosts file (with 16K+ entries) to combat website ads. Each entry in the /etc/host file had the form: 127.0.0.1 <hostname>.

AppleJack has been updated to work with Snow Leopard with the release of version 1.6.

In a nutshell, AppleJack is a command-line utility and series of scripts for running repair tasks in Single User Mode when a bootable startup disc in not available. It's great for those times when all you get is a blue screen and no GUI startup, and need to troubleshoot and repair the problem, but left your complete CLI reference book in your other suit.

To use it, bring up Single User Mode by holding down Command-S at startup and then when the prompt is available type applejack. Use the menu provided or select 'auto pilot' to perform all of the basic tasks, such as filesystem and permission repair, cache clearing, and more. There is an 'Expert mode' available by typing 'x' at the AppleJack prompt to do more operations on the hardware and user accounts. Documentation is provided in a Man page; type man applejack for that.

This version supports 10.4 and up. Since Apple usually changes things under the hood with each major OS release a tool like AppleJack has to be updated for compatibility, so older versions didn't function properly in 10.6.

For more details, there was an excellent review of the previous version on Macworld. This will give you a good feel for this tool.

[crarko adds: I tested this, and it works as described. I swear by AppleJack, and am delighted it's finally 10.6 friendly. Just remember it needs to be installed before you have trouble, and not after the fact.]

There is finally a way to cut and paste files and merge folders in Snow Leopard. A new (shareware) Mac menu bar application, called moveAddict, provides this function, so you can use Cmd+X and Cmd+V in the Finder.

If you are experiencing a condition where the Console freezes when launched, and/or Terminal is very sluggish when starting up, it may be due to an accumulation of log files.

This blog post by Shannon Hicks shows how the problem was traced to a glut of hundreds of log files in /private/var/log/asl. [crarko adds: I just looked at my Mac, and there are only about 25 files in mine. That seems to be OK.]

If you don't need to keep these logs for some other reason, they can be deleted using the Terminal command:

sudo rm -f /private/var/log/asl/*

[crarko adds: I haven't tested this one. If you don't have the issues described, it's best just to leave the log files alone. See the comments below for more information about the log rotation process.]

Are you used to hiding windows instead of minimizing them because Command+Tab switching to an application does not bring up the document window?

When searching for a solution to this the only things that came up were applications like LiteSwitch and Witch. A bit of the functionality is also available in the built-in application switcher, but it's well hidden.

When you are cycling applications with Command+Tab, find the application you want to activate and press Option, then release the Command key and the window will un-minimize. Maybe there's a way for this to become default behavior by doing a defaults write command in Terminal, but I don't know how.

[crarko adds: I tested this, and it works as described. It seemed to only open the most recently minimized window if there were several. There is an earlier hint about modifier keys, but it doesn't mention this function.]

Fast User Switching has a lot of benefits, but one of its downsides is that it is easy to end up with multiple users in the background wasting system resources and needlessly degrading performance. This hint shows how to implement a system to log out users automatically if they have been sent to the background for a specified period of time.

In order to keep the benefits of Fast User Switching while avoiding the situation where multiple users remain logged in unnecessarily, it is necessary to have a way to cause users to log out automatically after being in the background for a period of time. Unfortunately, Mac OS X does not provide a way to do this. (There is a setting in the Security preference pane for logging out automatically after a certain amount of idle time, but it logs out all users and only does so when no one uses the computer for the specified period of time; so long as anyone is using the computer, all background users stay logged in.)

[crarko adds: OK, there are some serious questions raised about the procedure described below. I suggest waiting for further corroboration before trusting it.]

Here is some background on the recent announcement about a piece of malware which has been found to affect Macs. The spyware in question is called OSX/OpinionSpy and it’s a new variant of Windows spyware that has existed since 2008.

This link (to The Guardian) offers a manual method to remove the spyware which was installed with the screen savers from 7art, or other infected applications which may have been installed.

To see if you're affected, run Activity Monitor (in /Applications/Utilities) and set it to show All Processes in the dropdown menu. Look for a process called 'PremierOpinion' which will be owned by root. If it's there, you've been affected.

To summarize the removal procedure:

• Go to the /Applications folder in the Finder.
• Find the PremierOpinion folder.
• [crarko adds: Possible dangerous step removed.]
• Move the PremierOpinion folder to the Trash and empty the Trash; if won't delete, choose 'Empty Trash' while holding the Option key. You may need an administrator password. Reboot the Mac after doing this.
• Check again in Activity Monitor to be sure the process 'PremierOpinion' is no longer there.

The submitter expresses thanks to Paul Mortgaat on the X4U mailing list for pointing out this tip.

[crarko adds: Thankfully, I haven't tested this one. I've removed one step in this procedure until it can be verified as not making the problem worse. And take a look at the procedure mentioned in this comment as a more comprehensive operation.]

I was looking for a way to change the creation date of a file and I found this hint, and through that, the ChangeFileDates command line tool at hamsoftengineering.com. I noticed that ChangeFileDates will accept some pretty vague relative dates as valid inputs!