So here we are, at the end of OS X. Two decades ago Apple parked the sixteen-year-old Classic Mac OS and leaped to version 10.0, but four years ago the company rebranded the software that drives the Mac as macOS, and the writing was on the wall. And now in 2020 it’s macOS Big Sur, version 11.0. The name is an extension of Apple’s use of California places to brand its Mac releases, but the version number is the real story. The Mac OS X era is truly over. macOS Big Sur is the start of a radically new era in the Mac’s life.

• “du –max-depth” alternative on Mac OSX Mattias Geniar, December 11, 2017. It features the latest news, guides & tutorials and new open source projects.
• If your Mac is using an earlier version of any Mac operating system, you should install the latest Apple software updates, which can include important security updates and updates for the apps that are installed by macOS, such as Safari, Books, Messages, Mail, Music, Calendar, and Photos.

With the release of the macOS Big Sur Public Beta, Apple is inviting users to get a head start on the journey that will eventually lead to Macs running Apple-designed processors and software built for iPhones and iPads alongside apps made specifically for the Mac. With huge changes to Mac hardware looming on the horizon, Apple has made the biggest design changes to macOS since the launch of Mac OS X.

Last year’s macOS Catalina felt like a release designed to settle old scores and clear the field for future advancement. It broke a lot of old software, frustrated a lot of users, and generally had the worst reputation of any macOS update in a decade. (I see you, Mac OS X Lion.) Did Apple sacrifice Catalina so that future OS updates wouldn’t be blamed for them? That’s probably a conspiracy theory too far, but I will say this: Good Cop macOS Big Sur fills me with excitement about the future of the Mac in a way Bad Cop Catalina never did.

Operating System Mac® OS X 10.15 (Catalina) or higher (latest version) Processor Intel® Core™ i3 or better Video NVIDIA® GeForce® GT 650M or ATI Radeon™ HD 5670 or better Storage 25 GB available HD space Internet Broadband Internet connection Resolution 1024x768 minimum resolution.

The new macOS design

When Apple makes major operating-system design changes, they tend to start out a bit extreme and then get beaten into shape over time—until they become boring and are replaced by a new design. There are definitely some aggressive, challenging changes in the macOS Big Sur design that will throw long-time Mac users for a loop. And I expect that some of them will end up getting re-thought by Apple’s designers, if not this summer than over the next couple of years.

That said, a lot of aspects of the Big Sur already feel comfortable—probably because I also use an iPhone and an iPad (as do most Mac users) and Big Sur is picking up aspects of the design of those devices. Big Sur’s design has a lot of rough edges, but it also has a lot of potential.

High-contrast windows

If the atom of the Mac interface is the window, then Apple has split the atom in Big Sur. The first time you look at a Finder window in Big Sur, you will realize that the Mac you have known for years is gone. Let’s start with the sheer lightness (or in Dark Mode, darkness) of it all: the gray gradient of the title bar and toolbar is gone, replaced by a white (or very dark gray) space that’s populated with the contents of both the title bar and toolbar, collapsed into a single row of items. Toolbar icons are simple glyphs that only gain an outline when you mouse over them. The title, once centered, has been aligned to the left and made bolder, with its icon hidden (until you mouse over). The Back and Forward buttons are perched on the extreme left, even beyond the title of the window. The Search box is now gone, collapsed by default—you must click the Search icon to make it appear.

Apple has also altered the geography of the window itself, in a move that was telegraphed with the design of several apps, including Music, Podcasts, Reminders, and Maps, in macOS Catalina. Previously, a normal Mac window was best thought of as a single space with a title bar and toolbar spanning its entire width, and within it could be a content area or a sidebar and content area. But if you have a window with a sidebar in Big Sur, the geography is different. The window is instead sectioned in two, with the sidebar and the red/yellow/green “traffic light” buttons on the left (with a slightly translucent background), and the title bar, toolbar, and content area on the right.

SF Symbols, Apple’s library of glyphs, has been added to macOS with Big Sur, and it lends an air of consistency to toolbars and sidebars. The appearance of colored glyphs in sidebars—favorites in the Finder are blue, for example—is a pleasant addition. Even the venerable “disclosure triangle” that you can click to reveal the contents of a folder has been reduced—it’s lost its third edge and its gray fill color, and is now just a carat. (It also appears in sidebars as a way to collapse or expand lists of sub-items, replacing the word “Hide” that appears in Catalina.)

While the density in the toolbar has gone way up, the rest of the window has spaced out. There’s much more space between the red/yellow/green “traffic light” buttons and the edge of the window, and the same is true of the additional white space above and to the right of the title bars/toolbar.

The windows of apps that haven’t been updated to support this new format will receive a more minor makeover. The title bar will be white (or dark gray), and the title font is now bold, but the title is still centered and there’s none of the additional padding that’s been added to new-style Big Sur windows.

Make room for Big Sur

Adding more padding is a recurring theme in Big Sur. Apple has also made the menu bar taller (as well as making it distractingly translucent). The menus themselves now sport curved edges at the top (which seems wrong metaphorically?), and there’s additional space between each menu items.

The big question is, does this mean that Apple is preparing for a future where Mac screens also support touch input, so that you could navigate a menu with your finger in a pinch? It sure feels that way, but I’m open to the possibility that Apple just thinks that our displays are big enough now that they can afford to look a little less cramped. I wonder what this design decision means for the future of tiny Apple laptops. I know I’d be frustrated if my old 11-inch MacBook Air was this inefficient with space.

It also feels that everything in Big Sur is rounded at the edges, from windows to menu items to alerts to the Dock to the icons… it’s consistent, and in keeping with most of Apple’s hardware designs, which eschew sharp edges. It makes me wonder why Apple didn’t just mask the corners of the screen in Big Sur (as they were on the original Mac) to make them feel equally curved. The right angles at the corner of my display seem awfully jarring when I’m using Big Sur.

Speaking of icons, I should mention that Apple has redesigned all of its app icons and appears to be all in on making the iOS-style rounded rectangle the standard on macOS as well. Every single Apple icon is a roundrect, and given that future Macs will be able to run iOS and iPadOS apps, perhaps it makes sense to strive for some sort of icon harmony.

That said, Apple’s icons are peculiarly inconsistent when it comes to items placed in front of the roundrect, such as the (outmoded) hard drive in Disk Utility, the loupe in Preview, and the chess piece in Chess. Not only do these items break the silhouette of the roundrect shape, which spoils the entire point, but they’re not even placed consistently—they’re all viewed from somewhat different perspectives.

I’m also not sold on some of the additional detail Apple has added to the icons. Apple says that the level of detail in the new Mac icons is intended to be an homage to the rich icons from OS X’s past. But at most sizes, the added shading to the Messages icon just makes it look dusty. And I guess adding a line of text on the back of the Mail icon’s envelope is a fun easter egg, but at certain sizes it’s just a nondescript line that kind of looks like a mistake.

If you happen to be someone who designs app icons, though, you will be cheering. One look at the Dock in Big Sur will tell you who has gotten with the program and who is, in the words of Steve Jobs, a “laggard app.” Circles? Random shapes? They stick out like sore thumbs. Apps with existing iOS counterparts will probably just use versions of those icons; every other Mac app is going to need a roundrect icon update to avoid looking hideously out of step with the times.

The Dock itself has, of course, also gotten a makeover. It’s more translucent (which is fine, since there are no legibility problems with icons like there are with text in the menu bar), it’s floated away from the edge of the window (there’s that trend toward more padding again), and of course the corners are aggressively rounded.

Revolution in the menu bar

Another major change to macOS is happening in the upper right corner of the menu bar, where Apple has introduced Control Center and redesigned Notification Center. Both of these moves have a lot of potential, but I’m less impressed with the execution.

When you click on the new Control Center menu bar item, you’ll see a Mac expression of the Control Center concept that’s been on the iPhone and iPad for a while now. Essentially, Apple is grouping a bunch of common device controls in a single sub-menu, rather than putting them all under individual menu bar items. If you do want an individual menu bar item for a particular control, you can drag it out of Control Center and into the menu bar to add it. (But it remains in Control Center, too.)

Control Center offers controls for Wi-Fi, Bluetooth, AirDrop, Do Not Disturb, keyboard brightness, AirPlay Display, display brightness and related controls, volume level and other sound controls, and a Now Playing item for media control. Many of these controls are simple sliders and buttons, but when you mouse over them you’re offered a carat symbol that leads to more in-depth settings.

It’s a nice idea, but the execution is a mixed bag. You can remove some items from Control Center (via the Dock and Menu Bar area in System Preferences), but not others. I like the idea of pulling a lot of stray icons out of the menu bar, and giving users a single place to go to adjust a lot of device settings. But there needs to be more customizability and consistency.

To access the new Notification Center, you click on the clock in the menu bar, rather than the previous Notification Center icon. I’m all for reducing menu bar clutter, but this doesn’t make sense to me. Notification Center isn’t related to the clock in any way. This is Apple attempting to cut corners and hide one thing underneath another in order to save space. There should be a Notification Center menu bar item, separate from the clock.

Appearing underneath the clock when you click on it (or if you swipe from the right edge of a trackpad) is a remixed Notification Center that’s a lot better than the previous version. Gone is separation between Today and Notification views—there’s a single view with notifications at the top and widgets below. Notifications are now grouped by app and they’re limited to a few slots, with a button to view more notifications below them, so they don’t consume all the space. It’s a more iOS-like approach, and it’s an improvement, though I feel like I’ve never really properly used Notification Center on the Mac and I’m not sure this will improve matters.

Below the notifications is where the fun really begins, though. The new-style widgets from iOS 14 and iPadOS 14 are also present in Big Sur. Widgets come in three sizes and you can configure them to display how you like. I doubt that the Mac will ever be as big a home for widgets as iPhone or iPad, but I’m glad they exist. It might be nice if you could choose to drag widgets out of Notification Center and plop them on your Desktop, too. But it’s a nice addition to macOS that also brings across some family unity with Apple’s other devices. If you like that weather widget you’ve got on iOS, you can get in on your Mac, too.

It’s early days in beta season so I won’t judge Apple’s widgets too harshly, but they do seem a bit buggy. I was unable to reorder cities in the World Time widget, for example, and sometimes widgets didn’t seem to be serving out updated data. I hope that Apple works the bugs out over the summer.

App changes

As always, a new operating system means changes to many of the apps Apple includes with the operating system. This year Apple has made a bunch of changes to Safari—which, for those of us who don’t use an alternate web browser, might just be the most-used app on our Macs. There are also new apps that have been imported from iPadOS via Mac Catalyst, and a raft of other changes. Here are some of the highlights.

Safari

I am a loyal Safari user, across all of Apple’s platforms. And I’ve got an admission to make: I use the Start page. That page that feels like the web-browser equivalent of a super-uncool, AOL-start-page, MySpace-using, “gateway to the ‘Net”? That Start page. I don’t use it exclusively—on the Mac, at least, I also keep a row of toolbar favorites visible at all times. But I have gravitated toward using it on my iPad, and that has in turn trained me to use it more on my Mac, too.

In Safari 14—which, as is generally the case, will appear not just on Big Sur but will also be available for macOS Catalina and macOS Mojave—the Start page has gotten a nice upgrade. You can now customize it with a background image of your choosing, which is fun, but you can also click on an icon in the bottom corner of the screen and choose which sorts of items you want to see in the Start page: Favorites and Frequently Visited, of course, but also Siri Suggestions, Reading List, and the new Privacy Report feature that sums up what Safari has been doing to prevent anyone from tracking you from site to site.

Privacy Report also appears in the Safari toolbar by default. Click on it when you’re on any webpage and it’ll give you a report about how many cross-site trackers that Safari encountered. There’s not really anything you can do with this information, so it’s more of an advertisement for Apple’s laudable attempts to guard the privacy of its users than an actual feature unto itself.

I’m also not a fan of the way the information is presented by Privacy Report: It lists how many “trackers prevented,” but it’s not actually preventing the “trackers” from working—it’s just preventing the information they gather from tracking you when you visit different sites. And many of the “trackers”, like Google Analytics and ChartBeat, are arguably not trackers at all.

I’m also a bit disappointed that Apple didn’t go the extra mile and have the Privacy Report widget display a score or grade for the privacy features of any particular website. That’s what DuckDuckGo’s Safari extension does, and while the user can’t really do anything with that information other than complain or choose not to go to that website ever again, at least it would have some name-and-shame value that might motivate websites to be better citizens.

Safari is finally catching up to Google Chrome with the addition of in-place translation across seven languages. Once Safari detects a foreign language, it will display a translation icon in the search bar. Once you’ve clicked to see a translation, any additional pages you visit on that site will automatically load in translation while you’re there. Apple is launching with support for seven languages, including English, Spanish, Simplified Chinese, French, German, Russian, and Brazilian Portuguese.

Safari 14 also completely embraces the website favicon in browser tabs. If you don’t remember the debate about this feature from back in 2017, the short version is that for ages now Chrome has included a small website icon in its browser tabs, along with the name of the page. Safari didn’t used to show the icon, though it now lets you optionally display it. In Safari 14, favicon display is on by default, and Apple has improved legibility when you’ve got a lot of tabs open by collapsing tiny tabs down to only display the icon. Apple has also added a quick page preview when you hover the pointer over a tab, letting you see what’s there before clicking.

Finally, Apple is adding support for the popular WebExtensions API that’s used by developers to write plug-ins for other browsers, such as Chrome and Firefox. Theoretically, this will allow Safari users to finally take advantage of all of the cool extensions written for those other browsers. But of course, there’s a catch. For an extension to work in Safari, the developer may need to make some changes in order to meet Apple’s security standards. They’ll also need to use Xcode (which means they’ll need to buy a Mac if they don’t own one), and they’ll need to submit their extension to the App Store.

That’s a lot of barriers just to reach Mac users running Safari who could just as easily open a different browser to get that functionality. It feels like the big inducement here is to be ready with Safari extensions for macOS and then rush into iOS and iPadOS the moment Apple supports these extensions on those platforms, too. But if you’ve got a favorite Chrome extension that you’d like to see come to macOS, you may need to write to the developer and try to convince them.

I hope Apple makes this work and Safari gets a much richer extension library out of this, but there’s also a scenario where plug-in developers just don’t bother with Safari. That would be a shame. We’ll see.

Catalyst moves ahead (at last)

Two years ago, in macOS Mojave, Apple began the migration of iPad apps to the Mac with four stock apps. Last year, Apple opened up the technology used to make that migration possible, Mac Catalyst, to all app developers. The results in the past year have been mixed. While a few interesting apps have come across, it’s been a relatively quiet migration. Developers I’ve talked to have cited the limitations of Catalyst, and expressed hope that it would be improved in Big Sur.

Early indications are that it has been improved quite a bit, and maybe this will finally bring a much larger number of iPad-only apps to the Mac at last. Perhaps one reason for the improvement during this cycle is Apple’s replacement of two prominent Mac apps with new Catalyst versions: Maps and Messages. Apple might’ve been able to sneak by with an iffy implementation of Catalyst for a bunch of apps that hadn’t existed before on the Mac, as was the case with previous Catalyst apps, but with Maps and Messages each feature regression would be an indictment of Catalyst.

So I’m happy to report that my early experience with both apps is good. They feel like Mac apps, albeit with an iPad sort of flavor. Catalyst now supports multiple windows, so you can pop out a chat from Messages into a separate window without any trouble. The date and time pickers are no longer spinning wheels, which was perhaps the most glaring example of Catalyst’s unfinished nature.

And then there’s the upside: Apple’s been adding features to both Maps and Messages over the years—and just not bringing them to macOS. With the move to Catalyst in Big Sur, we finally get access to those features on the Mac. If someone on an iPhone sends you a message with lasers, you will see the lasers. And can respond with balloons. This isn’t just the case where the Mac is getting this year’s Messages improvements (like pinned chats, threading, and mentions)—it’s getting those, and last year’s improvements, and the previous year’s, too. The same is true for Maps, which gets this year’s feature additions like bike directions, but also previous iPad features like street view.

Now, let’s be clear: Getting this version of Messages is only a cause for celebration because Apple essentially abandoned the Mac app for several years. And the same is true, to an extent, to Maps. I don’t want to praise Apple too much for these new apps, because it was shameful that these core system apps (especially Messages) were kept in stasis, buggy and behind the times, for so long. But at least now, they will move in lockstep across Apple’s platforms—and that’s fundamentally good for the Mac.

This is really a glimpse into the future of the Mac, too. Mac Catalyst really exists because Apple doesn’t want to (or can’t afford to) maintain separate apps for the Mac and iPhone/iPad. Now Apple—and any other developer who wants to take advantage of Mac Catalyst—can start looking at the Mac as an additional place for their iOS development work to go. I think in the end this will be a net benefit for the Mac.

And the rest

There are dozens of other feature additions in Big Sur, and I look forward to spending the rest of the summer investigating them. A few stood out, though.

Reminders gets a bunch of new features, including the ability to assign items to people in a shared list. Photos has improved its Retouch tool to use machine learning, which has the potential to dramatically improve that feature.

And if you use a laptop with Big Sur, you get access to the very nice Battery system preferences panel, which displays some graphs of your battery level and usage in the last 24 hours and 10 days. (Desktop users will instead see the classic Energy Saver panel.)

Apple has revamped the system sounds, both beeps and other sound effects. We went over many of them in a recent episode of Upgrade, and while some of them are improvements, others feel like real downgrades. I guess we’ll all get used to them.

Of course, perhaps the biggest feature of macOS Big Sur aren’t even really available to the general public yet: support for Macs running Apple silicon rather than Intel. This is the first version of macOS that will support those Macs, when they begin arriving later this fall. I’d imagine that we may see some special macOS features that are only enabled on those systems and that Apple is holding close to its chest in the meantime. (I’m fascinated to see just how the process of downloading iOS apps and running them on a Mac feels, for instance.) But it’s worth remembering that this isn’t just a normal macOS release, but the first release that offers compatibility with an entirely different processor architecture.

How big is Big Sur?

It’s still early yet. There are probably months to go before macOS Big Sur makes its way to people who haven’t signed up for beta testing, and there are rough edges here, to be sure.

But overall, I think this is an exciting time to be a Mac user. Yes, Big Sur looks and feels very different from the Mac we’ve all come to know. But that’s part of the excitement. I’m excited that Apple is shaking up the Mac after many years of complacency. If you’re not excited by this, I understand it—and Catalina (and let’s be honest, Mojave) is there for you in the meantime.

I’m happy that the Mac has more life left in it, and Big Sur feels like the start of the next phase. With it, Apple is redefining how we use our Macs and the software on them while preparing for a new generation of Macs running Apple-built processors. If Catalina was a bitter taste of medicine, maybe Big Sur is the reward.

If you appreciate articles like this one, support us by becoming a Six Colors subscriber. Subscribers get access to an exclusive podcast, members-only stories, and a special community.

Home > Articles > Apple > Operating Systems

1. The Layers of Mac OS X: Darwin

The Layers of Mac OS X: Darwin

Now you delve into the deepest layers of Mac OS X. The umbrella name for this layer is Darwin. Darwin is open-source code, which means that Apple makes the code publicly available (http://www.publicsource.apple.com/). This availability allows developers to better understand the code as well as modify and improve it. Darwin is sometimes referred to more generically as the Mac OS X kernel environment.

In discussing the layers of Mac OS X, what determines whether something is considered to be at a higher or lower level? The answer is that as a general rule, a component at a lower level is used by all higher-level layers. But the converse is not necessarily true. Thus, an application, whether it is Carbon and Cocoa, uses the core Darwin technology, but Darwin can function without a need for any additional application layer.

Darwin is the core of Mac OS X. The Darwin kernel consists mainly of the FreeBSD and Mach 3.0 technologies. Darwin includes various core services, such as those involved in networking and device drivers. I discuss this topic in more detail in Chapter 5, as I walk through the startup sequence of events. Beyond that, as an end-user troubleshooter, you need be aware only of the two key kernel components.

Mach

As a troubleshooter, you will rarely, if ever, be working directly with Mach code. Nonetheless, it is important to understand its basic concepts. Mach refers to the code that handles the most fundamental aspects of Mac OS X. It is also responsible for several of Mac OS X's most touted benefits:

Preemptive multitasking. This term refers to how Mac OS X can schedule its processor activity among different open applications or processes. (All applications are processes, but not all processes are user-accessible applications.) Mac OS 9 used cooperative multitasking, which was not very intelligent. In Mac OS 9, unimportant but CPU-intensive background events might take up so much of a processor's time that more important activities in the foreground would become sluggish and unresponsive. Neither you nor the OS could do much about this situation. Mac OS X's Mach has much more flexibility in how it handles these matters. In essence, it can preempt any running process, giving something else more attention. It can note intelligently what activities are in the foreground and make sure that they get the lion's share of attention. Developers can also write hooks in their software to increase (or decrease) the priority that their software should get. As a result, operations that need the most processor activity at any moment should get the most, enhancing overall performance. This is a good thing.

A related benefit of Mac OS X's multitasking capability is that fewer modal functions prevent you from doing other tasks. That is, Mac OS X offers multithreading. In Mac OS 9, when you launched an application, you typically had to wait for it to finish launching before you could do anything else. This process could take a minute or two. Mac OS X doesn't have these waiting games. Instead, once a program starts to launch, you can begin another activity right away. You could check your email while waiting for Classic to launch and Photoshop to open, for example.

Protected memory. Metaphorically, protected memory means that the memory assigned to each open process is entirely separate (protected) from that of every other open process. The result is that systemwide crashes should almost vanish from the landscape. If and when an application crashes, it should cause only the application itself to go belly up; the rest of the operating system should remain functional. In the event that a program freezes (such as when you get an endlessly spinning beach-ball pointer), you will still be able to switch to a different program (such as the Finder) and continue to work as normal, even while the problem application remains frozen. This would be impossible to do in Mac OS 9. Protected memory also means that you should almost never need to restart the Mac to recover from a crash.

Virtual memory. Virtual memory allows you to simulate memory (RAM) via a special file on your hard drive. The main advantage of virtual memory is that if you do not have sufficient physical (built-in) RAM for what you want to do, you may get the RAM boost you need via virtual memory.

In Mac OS 9, you could choose to turn virtual memory on or off. As virtual memory tended to slow performance, it typically was wise to turn it off if your physical RAM was more than adequate for your needs. In Mac OS X, virtual memory must always remain on. Until you really start pushing its limits (by having way too many applications open at the same time, for example), you should not notice a performance hit.

Still, you can't have too much physical RAM. And given the current low prices of memory, I would recommend buying as much RAM as you think you will ever need—or more.

Dynamic memory. In Mac OS 9, the amount of memory assigned to an application is fixed (or static) when the program is launched. You assign this fixed amount via the Memory settings in the application's Get Info window. After an application was launched, if it needed more or less memory than was assigned to it when it launched, the OS could not do about the situation. You had some limited ability to add RAM assigned to an application, via an OS feature called temporary memory, but not all programs could use this feature, and it did not solve the problem completely.

One result is that you would still wind up getting 'out of memory' error messages in Mac OS 9, even when you technically had enough memory available for what you wanted to do. The OS could not shuttle the memory around to where it was needed at the moment.

In Mac OS X, memory assignment is dynamic, which means that the amount of memory assigned to an application can be increased or decreased as needed. Thus, if an application is idling in the background and hogging unused memory, the OS can grab some of this memory for another application that needs it more. The combination of dynamic memory assignment and Mac OS X's virtual memory means that you should almost never see 'out of memory' error and should have fewer memory-related system freezes and crashes.

Similarly, the total amount of memory available as virtual memory can be adjusted on the fly in Mac OS X. You could not do this in Mac OS 9. Making a change in the total size of virtual memory required restarting the Mac.

Mac OS X manages all these tasks and also allocates memory intelligently from physical and virtual memory so as to maximize the performance of each application. Still, as I implied earlier, memory availability in Mac OS X is not infinite. If you push your Mac to its memory limits, you will start noticing an overall decline in the performance of everything. Applications may succeed in opening without an error message, but you will still see the effects of too-little memory. That's why getting more physical RAM still makes sense.

NOTE

Mac OS X's Show Info window still includes a Memory tab for Classic applications, because Classic applications do not take advantage of Mac OS X's dynamic-memory feature.

Figure 4.4 The Memory tab of the Show Info window for a Classic application.

BSD (Unix)

Mac Os Download

BSD stands for Berkeley Software Distribution. It used to be called the Berkeley version of Unix but is now referred to as BSD, so referring to it as Unix is a bit incorrect. For all practical purposes, however, the term is synonymous with 'a version of Unix.' A portion of the Mac OS X kernel is based on FreeBSD, a version of BSD.

Note: Part of the BSD installation is optional when you install Mac OS X. The optional component is installed by default, however, unless you do a custom installation and choose not to install it. Overall, there is little cost (other than some disk space) in installing the optional files, and there are some Mac OS X features and some third-party software will not work without the files present. So I advise going with the default installation.

SEE

• 'Mac OS X: The down and up sides,' in Chapter 1, for background on why Unix is included as part of Mac OS X.

• Chapter 2 for more information on installing Mac OS X.

The integration of Unix in Mac OS X represents a significant change from Mac OS 9. In Mac OS 9, the System Folder was the OS. Except for a few invisible files (such as the Desktop files), all OS files were in the System Folder where they were easily accessible. In Mac OS X, the entire Unix layer remains largely invisible from the Aqua Finder. Thus, Mac OS X has a sort of secondary OS underneath the visible OS.

Occasionally, troubleshooting will require that you access or modify these hidden Unix files. One place where this requirement will likely crop up is file privileges. The Show Info window's Privileges settings are only a subset of the underlying Unix permissions that are really in use. The settings that you can't see can cause a variety of unexpected problems with opening, moving, or deleting files.

SEE

• 'Technically Speaking: Privileges vs. Permissions,' in Chapter 3, for more background on this subject.

• Chapter 6 for solving troubleshooting problems that require modifying privileges/permissions settings.

• Chapter 8 for more coverage of file sharing.

You access Unix commands and files in Mac OS X in three main ways:

Terminal. The Terminal application (included with Mac OS X) essentially provides a command-line environment where most Unix commands will work, just as though you were in a true Unix environment. Still, Terminal let's you know right away that you are not exactly in standard Unix, via its 'Welcome to Darwin!' greeting. Any changes that you make in Terminal, such as renaming or deleting files, will modify the Aqua environment as well, so you need to be careful.

Finder and text editors. Tasks such as moving or deleting Unix files can usually be directly done from the Finder. You can also modify some Unix files via text editors such as TextEdit and BBEdit. In many cases, this will require you to log in as a root user or use a utility that makes invisible files visible.

Aqua utilities. Via an Aqua-based interface, many third-party utilities allow you to more easily do what otherwise would require you to use Terminal.

SEE

• 'Take Note: Root Access,' in Chapter 3, for more information on logging in as a root user.

• 'Technically Speaking: Log Files and Cron Jobs,' in Chapter 3, for an example of accessing Unix invisible files from the Finder and via GUI utilities.

• Chapters 3 and 6 for several examples of how to access the invisible Unix files from the Finder.

• Chapter 10 for more information on understanding Unix and using Terminal.

TAKE NOTE

Cold Depths Mac Os Download

What and Where Are the Unix Files?

The 'system' software for Unix is located at the root level of the Mac OS X volume. You can see these invisible directories and files from the Finder by using a utility, such as TinkerTool, to make invisible files visible (as described more in Chapter 6).

Or you can use Terminal. To do so from Terminal, type: <cd />. Now type <ls>. This will list the contents of the root level.

Here is a sampler of the Unix directories and files found at the root level:

bin is the directory where most of the main Unix commands (or executables) are stored. These are the equivalent of what in Mac OS X would be called applications.

dev is where device drivers are stored. This are the files needed for your computer to interact with other hardware, such as external drives.

Mac Os Catalina

etc contains a mish-mash of administrative files.

tmp as its name implies, contains files created by programs that are only needed temporarily. Unfortunately, some programs may forget to delete these tmp files, so you may find some files here 'permanently.'

usr is another place where critical Unix OS commands are found, especially in /usr/bin. For example, the ditto and open commands are stored here.

mach is Unix's kernel, or core code, of the operating system. This is a file, not a directory. It is the software equivalent of the Mac's CPU, the central processing location for all Unix commands. Without the mach, nothing else would work.

Figure 4.5 Unix directories and files (for example, usr and bin) in the root directory, as viewed from (top) Terminal and (bottom) the Finder. The Unix items are normally invisible in the Finder; non-Unix visible items are also intermixed.

TECHNICALLY SPEAKING

gdb: The Mac OS X Debugger

In Mac OS 9, developers and some end users employed a program called MacsBug, mainly used by developers to debug software. In the event of a system crash, it could occasionally be used to recover from the crash without restarting. For this reason, and for a few other uses, it was a valuable troubleshooting tool.

MacsBug does not work in Mac OS X. The debugger in Mac OS X is gdb, a Unix tool accessed via Terminal. I will not be discussing its use further in this book.

TAKE NOTE

Folders vs. Directories

In Finder windows, you will see many icons that look like folders. Indeed, that is the Desktop metaphor for what they are: containers that hold other items (documents, applications, or other folders).

Folders vs. directories. In Unix jargon, a folder is referred to as a directory. And as Mac OS X has a Unix basis, I sometimes find it convenient to refer to these folders as directories, especially so when I am in a Unix environment, such as the Terminal application. Even in the Finder, I occasionally refer to folders as directories. I typically refer to the user's Home directory rather than Home folder, for example, because of the special significance that the Home directory has in Unix. (The directory is a default location where you log in via Terminal, for example.)

Thus, an Aqua folder is best viewed as being a graphical representation of a Unix directory. Moving an item in to or out of a folder in the Finder changes the underlying directory in Unix.The terms folder and directory are sometimes used interchangeably when the distinction is not relevant.

Note that not all Unix directories are displayed in the Finder. Most of them remain invisible to the Finder, because a typical Mac OS X end user will rarely, if ever, need to manipulate these files—and modifying them accidentally could lead to serious problems, including taking down the whole system. Still, as I said in the main text, I will cover throughout this book the essentials of how to access these files for troubleshooting.

Pathnames . A pathname is what Unix uses to define the location of a file or directory. An absolute pathname starts at the top or root level of the hierarchy and works its way down. /System/Library/Fonts/Geneva.dfont, for example, is an absolute pathname. Slashes separate the directory names. An initial forward slash indicates that you are starting at the root level. This setup is important, for example, in distinguishing otherwise-identical fonts in multiple Fonts folders (such as (/Library/Fonts vs. /System/Library/Fonts).

A relative pathname is the path starting from your current location.Thus, if you were already in the System/Library directory, the relative path to the same font file would simply be Fonts/Geneva.dfont.

The ~ symbol means to start at the top of the current Home directory. Thus, ~/Library/Fonts mean to look in the Fonts folder inside the Library folder inside your Home directory.

Because the forward slash is used in all these designations, you should not use the forward slash in the actual name of a file or folder in Mac OS X (much as the colon was not permitted in file/folder names in Mac OS 9).