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Or, how to defeat the password log-in for OS X
Ancient Mac tricks which still (usually) work today
REGULARLY BACKING UP YOUR IMPORTANT FILES
Always copying an important file or file update to a second disk or a USB memory stick or whatever is a MUST-DO for any serious computer user. People who don't back up their files probably shouldn't be allowed to use a computer at all-- for it's that damn important!
Computers and their related data storage mediums ARE NOT RELIABLE AT ALL, PEOPLE! That's why you must update copies of your important files onto extra disks or other contraptions every time you edit them.
Having important files on only a single disk or computer is plain dumb ass stupid-- unless you want to lose them.
Resetting PRAM
Resetting the PRAM on Macs today remains much the same as 20 years ago. Holding down the keys Command, Option, P, and R after switching on your Mac, and not releasing them until you've heard the startup bong at least 3 or 4 times (the Command key on a Mac usually has an Apple on it-- or else something resembling a four leaf clover).
Holding down this array of keys can be a bit of a challenging contortion.
Resetting the PRAM basically clears garbage out of a tiny bit of memory in your Mac that's responsible for remembering things like the date and time and which printer you prefer, even when the Mac is switched off. When that little bit of memory gets scrambled, various odd and annoying problems can occur with your Mac, until it's unscrambled again.
That tiny bit of memory usually has its own little battery to keep it alive, called the PRAM battery. When that battery goes dead, your PRAM problems tend to get worse. PRAM batteries tend to last only 2-4 years these days. On ancient Macs replacement PRAM batteries usually cost anywhere from $5 to $25. Those for modern Macs seem to be hovering around the $80 mark in many cases.
There's several Mac keyboard shortcuts users should be aware of: Mac OS X keyboard shortcuts
Making your Mac boot off a recovery CD/DVD instead of its internal hard drive
Hold down the C key at start up to make your Mac boot from a suitable CD/DVD already present in your drive.
Alas, getting your disk into that drive in the first place might be something of a challenge on a sick Mac which isn't behaving as you'd expect...
Fixing hard disk problems
Apple's disk utility, found either on your hard drive or your recovery disk, can fix many disk problems for you. Simply find it, open it, and follow the onscreen directions.
You'll basically have options to either repair the disk, or repair permissions. Or verify instead (verify is rarely useful).
Both types of repair may be necessary. And repeating the repair process a second, third, and fourth time might be necessary, too. As sometimes multiple passes are required to truly complete the job.
In those cases where repairs can't be performed or completed (and your Mac is still displaying undesirable behavior), you may have to resort to stronger measures. Like a complete erasure and re-installation of your OS from your recovery CD or DVD.
However, oftentimes a complete erasure won't be necessary, and you can simply put a fresh copy of your operating system on the disk instead, without affecting most of your personal data files on your disk. This partial solution is usually offered on your recovery CD/DVD, alongside the more extreme total erasure alternative. Just be sure you know which one you're using at the time(!)
Getting out of a frozen or unresponsive Mac program (force quitting).
This seems to be necessary a hell of a lot on modern Macs. Way, way too often. But as bad as it is today, it was even worse in OS X's first five years(!)
Steps (and alternative options) to take to force quit on a modern Mac (only go as far as you have to, to get to a normal condition again):
Keep in mind the command key usually has an Apple or four leaf clover-like symbol on it.
1. Go to the Apple Menu and choose Force quit...
2. Choose from the list presented the application you want to quit, the click the Force quit button.
3. Press option-command-escape.
4. Restart via control-command-power button.
5. Hold down the power button until the Mac shuts down (shouldn't take much longer than ten seconds).
Instantly turning a messed up Mac into an external drive for a second (but functional) Mac.
If you can get a damaged Mac to spin up its hard disk, you can bypass the hard drive's password protection plus access it like it's an external drive by using a Firewire cable and a second (but working) Mac computer. Connect the two with Firewire, power up the 'good' Mac, then power up the 'bad' Mac, making sure to hold down the "T" key on the bad Mac as it boots.
The bad Mac's hard drive icon should appear on the good Mac's desktop, with all files accessible there for copying over, or even moving around on the bad Mac remotely from the good one.
Booting up in safe mode during troublesome times
Holding down the shift key during boot will fire up the Mac in safe mode. In this mode, the Mac ignores many possibly problematic system extensions or drivers during the boot process, thereby often side-stepping whatever it is which might be preventing a normal boot up.
Booting in safe mode also takes longer than normal mode, as the Mac automatically does some disk checks and repairs then. In many cases those automatic repairs might fix everything themselves, allowing you to simply restart from a menu as you normally might (once the safe mode boot up has completed), and everything be fine again.
You'll still need your account password to get all the way into safe mode though.
PMU reset for dead or misbehaving Macs
This procedure might vary a bit between different Mac models.
Apparently a PMU reset is often necessary when you have an utterly dead Mac on your hands, which isn't responding at all to switching on the power button.
The PMU is basically the power management unit for your Mac (maybe only for portables), which tries to help you keep your battery topped off power-wise without causing it to explode (yes, quite a few modern laptop batteries have exploded in flames the last few years).
Apparently PMUs quite often go whacko on laptops-- but try to always err on the side of safety in their confusion. So instead of your laptop exploding into flames, it simply refuses to work at all. I.e., you're left with a dead laptop.
I had to try all the various PMU reset techniques repeatedly-- but in different orders-- to get one dead Mac laptop's hard drive to suddenly start spinning up again.
Even if these PMU resets don't get your hard drive spinning again, they might wake up the laptop enough to suck in the Mac OS X recovery disk when you try to insert it. And that can certainly help!
First PMU method
If the Mac's alive or turned on, shut it down/turn it off.
Pull the Mac's AC plug from the wall outlet or surge protector.
Remove the main battery.
Press and hold down the power button for five seconds (One-Mississippi, two-Mississippi, three-Mississippi, etc.)
Let go the button and replace the battery, then plug the power cord back in.
Second PMU method
Hold down shift-control-option-power buttons for five seconds.
Booting up in "single user mode"
Booting into single user mode allows you to type in commands directly to OS X while bypassing the usual graphical user interface.
Basically, you'll be in the UNIX version of the ancient DOS which PC users worked in for a generation. Where everything must be done via typed in commands which often look like gibberish to normal people.
Although this mode can offer you up some valuable and powerful alternatives to your Mac's normal interface, it also presents some major dangers. As a single error on your part could result in all sorts of havoc on your machine.
Thus, you must be extremely careful in single user mode, and sure about what commands you're using and why.
To enter single user mode, hold down the command/Apple key and "S" key at start up.
To exit single user mode, type "reboot" and press return.
The first few links below offer lists of commands for use in this mode. The rest deal with potential password and administrative access chores.
OS X's BSD/unix command-line Single-User Mode Commands
OS X's Single-user mode Commands
Troubleshooting with single-user mode
10.5: Reset a user's password in single user mode
Start up in verbose mode
Verbose mode in OS X basically displays on-screen what OS X is doing during boot up. This can be handy if you're suffering from certain types of startup problems, like kernel panics, because when OS X stalls out during boot, in verbose mode you'll see indications of the last things OS X was fiddling with before the crash.
In one real-life case of verbose mode help, I saw OS X crashed just after loading its Apple Airport drivers or extensions. It turned out the Apple Airport hardware had failed in that machine, so when OS X communicated with it via the extensions, the bad hardware response freaked out OS X, causing it to crash during startup.
Removing those extensions from the system folder enabled the machine to boot normally again (see this log entry for troubleshooting a Powerbook G4 for details)
To boot in verbose mode, hold down the command/Apple key and the "v" key during start up.
Last resort: disconnect the PRAM battery assembly deep inside your laptop
Note this trick can sometimes revive dead OS X desktops too. But it's much easier to extract a PRAM battery from a desktop to try it. In the switched-off desktop circumstance, remove the PRAM battery and let the Mac sit unused for 6-8 hours while its motherboard capacitors drain. Or even 24 hours if possible. After that you can re-install the battery and the Mac may boot up just fine. Keep in mind that a DEAD PRAM battery in a desktop is a different matter, and should be replaced.
After you've tried everything else with your OS X laptop (including all the above, such as formatting the hard drive and re-installing the OS), and you can still only boot up in safe mode, plus Apple hardware test says all your hardware including RAM is OK, and Disk Utility says the drive is OK, and the PRAM battery doesn't seem to be dead (your Mac can remember time and date), try this:
Near completely disassemble your Apple laptop in order to get to the PRAM battery assembly, then disconnect that assembly electrically from everything else, reassemble your laptop, and see if that fixed the problem.
Note this disassembly/reassembly process is torturous and fraught with risk: you may find yourself unable to put it all back together again in the end. Be sure to draw up a chart clearly labeling where each of the dozen or so screws go in the case for reassembly as you proceed. Taking notes and photos as you go might help. And be especially careful about the ribbon cable running from the keyboard to the motherboard!
For more about this awful exercise, see this real world account of a Powerbook disassembly to complete this very task.
So why not go ahead and buy a new PRAM battery assembly and replace the old one while you have everything in pieces? Because there's no guarantee it will fix your laptop. And the part could easily cost you around $100. The disassembly/reassembly process is necessary simply to test if this is the problem. If it turns out it was, you can live without a PRAM battery assembly by merely resetting your date and time and maybe printer preferences when necessary, and trying to avoid letting your main battery get too low on power (for that's when most resetting chores will become necessary). You'll also enjoy the bonus of this particular problem part never causing you such anguish again. The bonus detail is one big reason you might not actually want to have a functional PRAM battery assembly inside your laptop at all. Ever.
Of course, if you have plenty of money you can maybe avoid the disassembly/reassembly process by taking it in to an Apple dealer who will most likely say a motherboard replacement is necessary (that seems a standard reply if merely a couple recommendations on this page don't work), and charge you about what a whole new and better equipped PC laptop would cost you, merely to fix your old creaky Apple laptop. But you'll also end up with that damned PRAM battery assembly still connected inside your machine. Old or new, it's likely to eventually leave you with a dead laptop (again) that's incredibly difficult to revive.