Mac OS X Diary: Unix-The Gift That Keeps On Giving

It's probably happened to you once or twice. You get a great gift, something you've wanted for months. And right after you open the box and the various parts spill onto the floor, you notice the Some Assembly Required label. That's when you turn to the instruction manual, only to realize it's written in a language with only passing similarities to English.

Now you know how OS X users getting their first real taste of Unix feel. You can spend hours scouring the Internet for answers to your OS X questions, or you can turn here for some preliminary trouble-shooting tips. If the traffic on Macworld 's Operating System forum is any indication, Mac users are having some common problems and questions when they take the OS X plunge. These answers should help you with any initial hurdles; if not, be sure to stop by the Operating System forum, where I check in daily.

A Classic Dilemma

It's clear that getting into Classic is proving to be the biggest problem for OS X users so far. To use Classic-the OS 9.1 compatibility layer in OS X-you'll need to upgrade your current OS, be it 8.X or even 9.0, to 9.1. Apple includes an OS 9 CD in the box that will work fine if you haven't already downloaded the update. Without OS 9.1, Classic won't work; that's why Apple shipped the CD with OS X. Once you have OS 9.1 in place, you can reboot into OS X or, if you haven't already done so, install the new operating system.

Some users have reported problems upgrading to 9.1 from Mac OS 8.5 and earlier. The best workaround for that is to start your Mac up holding down the C key. That lets the computer know that it needs to start up from the CD or DVD drive.

Here's one last bit of advice after you've installed 9.1 and you're about to use Classic in OS X: be sure you've set up OS 9.1 the way you want it. Disable any extensions you don't need.

Getting to Your Roots

Some Unix-savvy Mac users have wondered how they can log in as root, a process that's changed since the beta. You really only need root access if you want to significantly alter your machine from the command line.

To enable the login for root access, you'll need to open the NetInfo Manager, found in the Applications: Utilities folder. Once there, you'll need to unlock the application-click on it and enter your password-to make changes. In the Domain menu, select Security and the submenu will give you the option to Enable Root User. You're all set. Now, you can log in as root using your password.

Everything Is Permissible

Once inside OS X, you may hit a snag when you attempt to copy or throw out a file; your Mac might not let you, giving a "You don't have permission" error message. Welcome to the fun world of Unix file permissions.

Each file has a set of permissions, or, to be exact, three sets of three permissions-read, write, and execute permissions for the file owner, group and world. You can adjust the permissions by going to Get Info and selecting Permissions from the drop-down menu. Still, that often doesn't solve the problem.

To truly tinker with file permissions, you'll need to journey into the brave, new-to-the-Mac world of Unix via the Terminal application, found in the Applications: Utilities folder. Or, you'll have to find shareware that can adjust your file permissions without you having to journey into the terminal. Check VersionTracker for a program called Get Info.

You can only change the permissions of a file you own. To get around this, you'll need to log in as root (see "Getting to Your Roots"). Then, launch the Terminal application. When it opens, drop the file you want to change on top of it. You will then see the path to its location on your hard drive directory in the terminal-which, for a directory called Brett, would look like /Users/brett/Desktop/filename. The filename, whatever it is, will always be the last part of a path.

Next, type cd/Users/brett/Desktop/filename. You should now be in that directory. Just to make sure, type pwd -- this lets you see the directory you're in. In this case, it would return /Users/brett/Desktop if I were in the correct spot.

Now for the fun part-setting your file permissions. File permissions are set using the chmod command-think change mode to help you remember-and a three digit binary code. The binary code is the important part-it also happens to be the most complicated. Remember that file permissions are three sets of three groups (owner, group, world). Each binary digit changes the read, write, and execute permissions to either on (yes) or off (no). On a chart, it looks something like this:

You need three of these digits to change the file-the first for the owner, the second for the group, the third for the world. Let's say you have a file named "brett_OS_X-diary.txt," and you want to share it with everyone. You simply type:

chmod 777 brett_OS_X_diary.txt

If you want only yourself and your group to read a file, only you to write it, and no one see it at all, you type:

chmod 640 brett_OS_X_diary.txt

I should mention the space problem in Unix-namely if your file name has spaces in it (such as "brett's OS X diary.txt"), then you need quote marks in the command line. The command on such a file would look something like this:

chmod 640 "brett's OS X diary.txt"

Now, isn't that Unix stuff easy?

Classic-You Can't Go Home Again

If you've ever had Classic crash-and it sometimes does that, just as OS 9.1 does-and can't get it restarted, venture into the Terminal application for a little under-the-hood troubleshooting. Once you're logged in, type the ps-ax command, which will list out all the running processes on your machine. Simply typing ps will list the processes you're currently running in the terminal.

You'll see an entry like the one below:

397 ?? R 136:24.40 /System/Library/CoreServices/ClassicStartup.app/Cont

The number 397 is what's known as the process ID, or PID. It will be different every time you restart Classic; new processes get new PIDs. Using the number in our example, you'd type:

kill -9 397

That way, you're killing what's left over from Classic. The -9 is a flag that tells the kill command you mean business, making it the best way to kill out of control applications.

If that doesn't work, check the system preference application under Classic, to make sure Classic has stopped running. If Classic is still going and you're running out of patience, you may be better off just restarting your entire machine. But, you shouldn't have to do that.

All in all, you'll find OS X a very easy-to-use OS. Don't be intimidated by the command line; it's only there if you need it-and I suggest you only use it if you are certain you know what you're doing. You can do a lot of damage in the command line, so be extra cautious when you're in there.

As for tackling those gifts with Some Assembly Required labels-that's a topic for a completely different diary.

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