If you like to go under the hood of Mac OS X, or if you've been forced to by quirky problems, check out our latest ebook, freshly revised for Snow Leopard: "Take Control of Permissions in Snow Leopard." Written by Unix guru and Mac aficionado Brian Tanaka (and edited by Geoff Duncan), the 91-page ebook mixes practical how-to details and troubleshooting tips with just the right amount of theory as it explains permissions in relation to how you keep your files private, copy files to and from servers effectively, set the Ignore Permissions option for external disks, repair default permissions, and delete those files that just won't die.

For those who want to learn advanced concepts, the $10 ebook delves into topics like the sticky bit, symbolic versus absolute ways to set permissions, and how to work with bit masks. Of course, Brian looks at what's new with permissions in Mac OS X 10.6 Snow Leopard, including the increased use of access control lists, changes to the way umask works, and which permissions a copied file ends up with.

Don't worry if you're not accustomed to using the Unix command line in Terminal, since Brian provides clear instructions for that, along with how to manage permissions from the Finder's Get Info and Inspector windows, and with a third-party utility, FileXaminer. (And of course, if you do want to become more familiar with the command line, we strongly recommend Joe Kissell's "Take Control of the Mac Command Line with Terminal," which provides a friendly and thorough introduction.)