Mounting an external drive when users are logged out in Mac OS X


In older versions of Mac OS X, you could create a special .plist file that auto-mounts disks even when a user isn't logged in. You can see that (no longer working) procedure here. I don't know exactly when support for that ended, but some people have suggested around Mountain Lion. (If you try it in Yosemite, your Mac will get stuck in bootup at Waiting for DSMOS if you run it in verbose mode... or just half a progress bar if you're booting it up in normal mode.)

People still want this feature, though. Here's a recent thread of frustrated people not being able to do it:
10 *still* requires users to be logged in for backup to work.

Major Prerequisite

I'm assuming you already know how to create a script. If you don't, use method #2 in Deleting Mac Keychains in an Active Directory Environment as an example.

Find the UUID of your external drive

There is a universally unique identifier for your drive. Unfortunately, the normal diskutil list command won't show it to you. Instead, when you launch up the, you should run this command (make sure the drive is physically plugged in before you run the command):

diskutil list -plist
and that will show you your external drive's UUID.

Highlight and copy the UUID.

Mount the drive via UUID

To do a quick test of mounting the drive, run a command similar to this:

diskutil mountDisk yourreallylonguniversallyuniqueidentifierfordrive
Whether that drive was already mounted or not, it should (if the command worked) display a message that says Volume(s) mounted successfully.

A visual example

Here you can see an example.

So fire up those launch daemons and go ahead and put that mount command into your script!

Getting started with pygame on a Mac

There are a lot of pygame tutorials out there, but I haven't yet found a simple, step-by-step how-to on how to just get pygame installed on a Mac, and then actually use it. So, hopefully, this will work for you. This example was done using Macs running OS X 10.10 (Yosemite). Your mileage may vary.

Installing pygame

Go to the pygame downloads page and scroll down to the Mac section.

Find the download titled Lion apple supplied python: and download and install it.

It says Lion, but it will work with Yosemite.

Creating a short sample pygame

Just so you can see how it works basically (and then later on, you can create/tweak your own games), here's one you can start with.

Open up a text editor (e.g., a terminal editor like nano or a graphical one like TextWrangler—avoid TextEdit, unless you know the difference between plain text and rich text).

Paste into the text editor the following:

import sys, pygame

size = width, height = 320, 240
speed = [2, 2]
black = 0, 0, 0

screen = pygame.display.set_mode(size)

ball = pygame.image.load("ball.gif")
ballrect = ball.get_rect()

while 1:
        for event in pygame.event.get():
                if event.type == pygame.QUIT: sys.exit()

        ballrect = ballrect.move(speed)
        if ballrect.left < 0 or ballrect.right > width:
                speed[0] = -speed[0]
        if < 0 or ballrect.bottom > height:
                speed[1] = -speed[1]

        screen.blit(ball, ballrect)
Save it to your desktop as

Then, save this beach ball image file to your desktop as well.

In (which you can find in /Applications/Utilities or using Spotlight), paste in this command:

cd ~/Desktop
This will change focus to your desktop directory (that's where you saved your Python script and your beach ball image).

Paste this command in next to run your script:


If it worked, you should see a beach ball bouncing around a black background.

Credit where credit's due

I didn't make up this tutorial out of thin air. This is a synthesis of a couple of online resources I found.

Movie projects disappear after iMovie upgrade

When you upgrade to the new iMovie, there's a quick prompt to update your old iMovie projects, but if you dismissed that and don't know how to go back and update again...

Go to File > Update Projects and Events...

More info at Apple:
Update projects and events from previous versions of iMovie in iMovie (2014)

Troubleshooting AirPlay to AppleTV

This is less of a step-by-step tutorial and more of "this is a situation we encountered and what ended up fixing it... your mileage may vary" post.

We had one laptop that had trouble connecting to one Apple TV in a classroom. My own laptop could AirPlay to it just fine.

When the non-connecting laptop would try to connect, sometimes there'd be an incorrect password error. Other times it would seem to connect (as extended display) but then not actually display. Trying to change from extended display to mirrored display would just keep it on extended display that wasn't really extending to the Apple TV.

I double-checked the Apple TV software was up to date. I rebooted the Apple TV. I rebooted the laptop. I tried taking the password off of the Apple TV AirPlay. No change after any of that.

Then I tried changing the broadcast name of the Apple TV, and the previously non-connecting laptop was able to connect! I changed the name back to the original name, and the laptop could still connect. I added the password back in, and the laptop could still connect.

So, I don't know if the renaming and naming back method will work for others experiencing AirPlay connectivity issues, but it's worth a shot!

Resetting a Windows password with ntpasswd

Proper Use Case

You may encounter situations in which you have forgotten the administrator password on a Windows computer, and you need to reset the password. This tutorial will walk you through how to reset it using an open source tool called ntpasswd.

Improper Use Cases

  1. If your Windows computer is joined to a domain, and you're trying to reset a domain account password, you need to do that through Active Directory. ntpasswd will not help you reset domain accounts, only local accounts.
  2. If you are trying to find out (instead of reset) an admin password, you cannot do so through ntpasswd. You may have some success doing so using Ophcrack, but it doesn't always work and may take a very long time. For more details on why, check out the FAQ page for Ophcrack.
  3. Try to break into an active (but locked) session. In order to use ntpasswd to reset an admin password, you have to reboot the computer. Really, you shouldn't be breaking into people's sessions anyway!

Download and use the USB / burn the CD

If you go to the ntpasswd website and scroll down, you should see some downloads available. There's one for USB, one for floppy, and one for CD. Even though you "waste" a CD, I think for first-time use of ntpasswd a burnt CD is the best way to go.

Download the .iso (disk image) zip file and unzip it.

Then you want to burn the .iso to CD as a disk image (not as data). For more details on how to do so, check out this tutorial, which uses a Ubuntu .iso as an example, but the same procedure works for any .iso, really.

Once you have the CD burnt, plop it into the optical drive for your old Windows computer and boot from the CD. You may have to press a special key during bootup (e.g., Esc, F12, F10, etc.) to get the computer to boot from the CD instead of its internal hard drive.

The actual password resetting

Once ntpasswd boots up, you'll see some special boot options.

You can type in boot and hit Enter. I believe you can even just hit Enter without typing boot. There are some special options, but try the default one first unless you run into problems.

ntpasswd will automatically scan the hard drive for any existing Windows installations. Some people have dual-boot Windows installations but in all likelihood you'll have only one, so you can just select the default by hitting Enter (otherwise, type in the number of the drive/partition you want, and then hit Enter).

Hit Enter, because you want to select Password reset [sam].

Hit Enter, because you want to select Edit user data and passwords.

You'll see a list of users. You can select a particular admin users you want to reset the password for. For the sake of this demonstration, we're going to use the built-in Windows Administrator account.

To select the user you want, type in the RID number. Since I'm selecting the Administrator account for this demo, I'm typing in 01f4.

In this particular case, the Administrator account is locked (which it is by default in Windows). So I'm going to type 2 to unlock the account. You do not need to do this most likely for any normal (not built-in) administrator account.

Type 1 to blank out the existing user password.

Type q to quit.

Type q to quit again.

This part is super important! When you're asked if you want to write the files back, you definitely want to type y to write them back, even though the default is n.

You may get a cryptic error that says cat: can't open '/tmp/disk': No such file or directory. Ignore it. It's probably fine.

If you're done with everything, type n to not run the whole process again.

When prompted, hit Control-Alt-Delete to reboot the computer, and then eject the ntpasswd CD so Windows will boot up.

You should now be able to click on the account (in this case, Administrator) to log in without a password.

Depending on your settings, you may just get a username and password prompt—in which case, enter the username and leave the password blank.

Wait to log in...

Go to the Control Panel and set or reset any passwords you want, now that you are again administrator of the Windows installation.

How many times do you have to write zeros or random data to a drive to securely delete data?

Conventional wisdom says that you need to do many passes of zeros, ones, combination of zeros/ones, and then random numbers in order to securely erase a drive so that its data cannot be recovered. But is this true?

The folks at HowToGeek make a good case for one pass of zeros being enough:
HTG Explains: Why You Only Have to Wipe a Disk Once to Erase It

From StackExchange, here is a shorter sum-up of the situation, though:
StackExchange answer to "Why is writing zeros (or random data) over a hard drive multiple times better than just doing it once?"

And an even shorter tl;dr version:
Summary: it was marginally better on older drives, but doesn't matter now. Multiple passes erase a tree with overkill but miss the rest of the forest. Use encryption.

The bottom line seems to be that there are some misinterpretations or misapplications of the Gutmann method, but more importantly that it's all about what can be done in theory. When it comes to practice, a single wipe of zeros is pretty much enough to take care of any basic data recovery methods.

If you're dealing with highly sensitive data, it probably still won't be recovered in any meaningful way after a single wipe of zeros, but you may not want to chance it, and end up doing several passes of zeros, ones, and then randoms, in addition to physically incinerating the drive.

DBAN's "autonuke" setting does three passes, and the nice thing about DBAN is that you can use it on pretty much any computer (it's a live CD or USB—so good for Windows, Mac, or Linux).

Mac OS X's Disk Utility has several built-in options.

If you launch up Disk Utility, select the drive you want to delete, and then click Erase, and then Security Options..., you'll see a pop-up window with a slider.

The first option doesn't do a secure wipe at all. It just "deletes" the data by marking it available for use.

The next option will be secure enough in 99% of use cases (e.g., you have a personal computer with family photos and other personal documents that will not financially benefit any criminals or politically benefit any governments).

This third option is about the same as the "autonuke" setting for DBAN.

And this last option—according to Gutmann himself, to HowToGeek, and to a bunch of other folks who've examined the issue closely lately—is just overkill.

A lot of the discussion you'll read in the links I posted above have to do with theory (could someone with limitless time and really expensive equipment possibly recover some tiny scrap of data from your hard drive) and a lot less to do with practicality. More importantly, it's difficult to track down actually successful (and verifiable) experiments of the theory [that traces of previous data exist even when you zero out everything or write random data over the previously existing data].

Practical security focuses a lot more on how badly criminal elements want your data and how difficult you make it for them to get to the data. If all a criminal gets is unusable scraps of what might have been a text file, and all that's really on the drive to begin with is some music, family photos, and Word documents, who is really going to spend hours trying to get that stuff back?

If, however, I have a computer with millions of people's financial data or with highly classified military documents... I'm probably going to do at least three passes before totally incinerating (Terminator 2–style) the drive. And that drive would have been fully encrypted to begin with.

As a simple, practical test, though, I did the second Disk Utility setting (one pass of zeros over the entire disk) on a 500 GB drive. Then I did data recovery on it using both Photorec and Recuva.

Here are the results...

Photorec took about 10 hours to scan the 500 GB drive, and it came up with 3 files—three .plist files and one .xml. I'm not 100% certain, but I believe those might be created by OS X itself when formatting the drive to HFS+

Recuva took a little over 2 hours to scan the 500 GB drive, and it came up with 3 files. Again, not 100% certain on this, but I believe those may be hidden files created by Windows when formatting the drive to NTFS (Recuva wouldn't recognize an HFS+ drive, so I had to use Windows' disk management to reformat the drive as NTFS before scanning).

If you're inclined to say 3 passes isn't enough...

  1. Make sure you know what you're disagreeing with. I am not (nor is the StackExchange response or the HowToGeek post) saying that a drive with highly sensitive documents should be disposed of after a single pass of zeros. Those should have been encrypted to begin with, have three passes, and then be incinerated. But doing the full 35 is overkill and, worse yet, doesn't offer any additional security over the three passes. So if you're going to disagree, disagree with the correct assertion. Don't engage in any of this business.
  2. I am, however, saying that for a basic home user with no extremely sensitive information (maybe some family photos and a handful of documents with no financial information), you can safely dispose of a drive after doing a three-pass on it (and, most likely, even a one-pass).
  3. Don't say "I have software that can easily recover one-pass deletions" without saying what software you use. I used Photorec and Recuva. If you believe another piece of software can actually recover data that's been wiped, say what software it is, and then prove that using it you were able to recover usable data after a one-pass or a three-pass.
  4. If you can recover fragments of data that are totally useless, who cares? If it's a text file, it has to have readable text. If it's an image file, it has to be a viewable image. You can't just prove that there used to be "in theory" data there previously, but it's data you can't recover.

I'd love to hear that I (and the wise StackExchange user, and Gutmann, and HowToGeek) are all wrong, but if that's the case... prove it.

Further reading:
Securely disposing data on hard drives and other storage media
The urban legend of multipass hard disk overwrite and DoD 5220-22-M
Overwriting Hard Drive Data: The Great Wiping Controversy

Fix for disk erase failed couldn’t unmount disk

If you're trying on a Mac using Disk Utility to erase a hard drive and it won't unmount, giving you an error similar to Disk erase failed. Couldn't unmount disk, then you may have to force an unmount through the terminal.

Launch up (through /Applications/Utilities or through a Spotlight search).

Then paste in the command:

diskutil list
to list out the different disks. You should see some disks appear like /dev/disk0, /dev/disk1, /dev/disk2.

Find the one you want to force unmount. For this example, let's say it's /dev/disk2.

Run a command similar to this one

sudo diskutil unmountDisk force /dev/disk2
If you're prompted for a password, enter it (yes, your account does need to have administrative privileges). You should not physically unplug the drive.

You should now be able to erase the drive.

Running sudo commands in Automator

If you're wondering how to run sudo (for privilege escalation) commands in Automator, this is one way to do it.

Launch up Automator (of course).

Find Run AppleScript in the library of actions.

Then, drag it over to the workflow area on the right. By default, Automator will put in some script structure for you to work with. Feel free to just delete that all completely.

In place of the predefined script, put in

do shell script "sudo whatevercommandyouwanttorun" with administrator privileges

if it's one command you want to run.

If you would rather run a script, it's a similar syntax of

do shell script "sudo /path/to/" with administrator privileges

You can save your workflow as an application.

When you double-click your .app file, it should then prompt you for an administrator username and password and then run your bash command or shell script in a sudo-like way.