Panic With The Lemon Mac OS

Kernel panics usually generate a file called a panic log. The structure and location of this file depends on the version of Mac OS X you are using: Under Mac OS X 10.6, panic logs are saved in the Macintosh HD Library DiagnosticReports folder. Note, during that period a Mac computer connected to the iPad via USB cable will NOT get ANY response because the ipad is completely off power. If you get a blank screen but you can see a glow when you touch the home button this confirms you have a charged battery and the iPad is booted up.

I’ve had my share of Macs over the years, most of them good (fortunately). I’ve never been stung by any of the more serious problems that have resulted from poor design, such as the iBook logic board problems or others. But today I’m writing about what I think is truly a lemon: the Mac mini.The Mac mini is a great idea: for $500, you get a relatively fast computer, one that is, above all, tiny and quiet. Designed probably to attract switchers from the Windows world, the Mac mini offers a limited feature set, but one that is largely sufficient for most users.

The Mac mini, as you know, comes naked in its box: no screen, no mouse, and no keyboard. This, again, allows switchers to simply hook up their existing equipment, or even use a KVM to switch between a PC and a Mac. This means that you have to make sure your existing peripherals work with the Mac mini. For a mouse and keyboard, this is no problem; the Mac mini will work with just about any USB devices (I haven’t heard about any incompatibilities, but it’s likely that any devices, especially mice or trackballs, that require drivers, will only offer basic functions unless there are Mac OS X versions of their drivers.

A kernel panic happens when something goes wrong in the kernel. As you can guess, the resulting behavior of your computer is the most unfriendly possible. The best you can hope for is that your computer stops in its tracks and prints out a string of obscure looking information, as it did in your case.
Aimed at consumers and professionals alike, Mac OS X aimed to combine the stability, reliability, and security of Unix with the ease of use afforded by an overhauled user interface. To aid users in migrating from Mac OS 9, the new operating system allowed the use of OS 9 applications within Mac OS X via the Classic Environment.

However, the real problem comes from the display. I guess that, in most cases, your display will work. You probably have a better chance of it working if you have a DVI display, as opposed to a VGA display. In my experience, however, the Mac mini is just not up to par for VGA displays. I have two Sony CRTs, about 2 and 3 years old. The first Mac mini I got gave a very dim display on one of them, and a green display on the other. No amount of adjustments, to either the monitors or the Mac mini’s Display preferences, changed these display problems. (Both these displays work perfectly well on other computers, one connected to an old iMac and PC, and another to a PC.) I was disappointed, especially when I saw all the problems on Apple’s discussions boards about display issues.

At this point, I was ready to just send it back for a refund – which was possible, since I bought it from an on-line dealer here in France who provides a no-questions-asked guarantee. But friends suggested that I try again, thinking that it could be just a bad unit, or a bad DVI-VGA adapter. Alas, when the second unit came, I connected it, and the same problems were present. Not it is entirely possible that my monitors are not “compatible” with the Mac mini; however, they are name-brand CRTs, with no special features that would prevent them from working with other computers (as I see daily at home). It seems that this is not an isolated problem: here’s a page on xlr8yourmac.com showing how common the problem is, and pointing out that the Mac mini simply does not put out enough power to drive many VGA monitors.

So, Apple’s got another lemon, and they’re clearly aware of it, but they don’t seem to be reacting to this widespread problem. Shame on you, Apple; at least you could set up a page saying which monitors you’ve tested the mini with so users can save all these hassles. You do this for some other devices, such as printers that are compatible with the AirPort Express, or CD/DVD drives compatible with iTunes.

Update, February, 2011: It’s worth noting that, since I first wrote this article in 2005, the Mac mini has changed quite a bit. And I also have a DVI display. In fact, as I wrote in this Macworld article, the Mac mini is now my Mac of choice. So the problems I highlight in this article, regarding video display, are no longer an issue.

A kernel panic message from a Linux system

Kernel panic in Ubuntu 13.04 (Linux 3.8) in Oracle VM VirtualBox

A kernel panic (sometimes abbreviated as KP^[1]) is a safety measure taken by an operating system's kernel upon detecting an internal fatal error in which either it is unable to safely recover or continuing to run the system would have a higher risk of major data loss. The term is largely specific to Unix and Unix-like systems. For Microsoft Windows operating systems the equivalent term is 'Stop error', resulting in a bug check^[2] screen that presents the bug check code on a blue background in early versions of Windows (colloquially known as a 'Blue Screen of Death' or BSoD), or on a green background on the Xbox One platform as well as in Windows 10 preview builds.^[3]

The kernel routines that handle panics, known as panic() in AT&T-derived and BSD Unix source code, are generally designed to output an error message to the console, dump an image of kernel memory to disk for post-mortem debugging, and then either wait for the system to be manually rebooted, or initiate an automatic reboot.^[4] The information provided is of a highly technical nature and aims to assist a system administrator or software developer in diagnosing the problem. Kernel panics can also be caused by errors originating outside kernel space. For example, many Unix operating systems panic if the init process, which runs in user space, terminates.^[5]^[6]

History[edit]

The Unix kernel maintains internal consistency and runtime correctness with assertions as the fault detection mechanism. The basic assumption is that the hardware and the software should perform correctly and a failure of an assertion results in a panic, i.e. a voluntary halt to all system activity.^[7] The kernel panic was introduced in an early version of Unix and demonstrated a major difference between the design philosophies of Unix and its predecessor Multics. Multics developer Tom van Vleck recalls a discussion of this change with Unix developer Dennis Ritchie:

I remarked to Dennis that easily half the code I was writing in Multics was error recovery code. He said, 'We left all that stuff out. If there's an error, we have this routine called panic, and when it is called, the machine crashes, and you holler down the hall, 'Hey, reboot it.'^[8]

The original panic() function was essentially unchanged from Fifth Edition UNIX to the VAX-based UNIX 32V and output only an error message with no other information, then dropped the system into an endless idle loop.

https://cooloload629.weebly.com/ryden-life-mac-os.html. Source code of panic() function in V6 UNIX:^[9]

As the Unix codebase was enhanced, the panic() function was also enhanced to dump various forms of debugging information to the console.

Causes[edit]

A panic may occur as a result of a hardware failure or a software bug in the operating system. In many cases, the operating system is capable of continued operation after an error has occurred. However, the system is in an unstable state and rather than risking security breaches and data corruption, the operating system stops to prevent further damage and facilitate diagnosis of the error and, in usual cases, restart.^[10]

After recompiling a kernel binary image from source code, a kernel panic while booting the resulting kernel is a common problem if the kernel was not correctly configured, compiled or installed.^[11] Add-on hardware or malfunctioning RAM could also be sources of fatal kernel errors during start up, due to incompatibility with the OS or a missing device driver.^[12] A kernel may also go into panic() if it is unable to locate a root file system.^[13] During the final stages of kernel userspace initialization, a panic is typically triggered if the spawning of init fails. A panic might also be triggered if the init process terminates, as the system would then be unusable.^[14]

The following is an implementation of the Linux kernel final initialization in kernel_init():^[15]

Operating system specifics[edit]

Linux[edit]

Kernel panic as seen on an iKVM console

Kernel panics appear in Linux like in other Unix-like systems, but they can also generate another kind of error condition, known as a kernel oops.^[16] In this case, the kernel normally continues to run after killing the offending process. As an oops could cause some subsystems or resources to become unavailable, they can later lead to a full kernel panic.

On Linux, a kernel panic causes keyboard LEDs to blink as a visual indication of a critical condition.^[17]Understanding slot machines.

macOS[edit]

When a kernel panic occurs in Mac OS X 10.2 through 10.7, the computer displays a multilingual message informing the user that they need to reboot the system.^[18] Prior to 10.2, a more traditional Unix-style panic message was displayed; in 10.8 and later, the computer automatically reboots and displays a message after the restart. The format of the message varies from version to version:^[19]