How to reset NVRAM on your Mac

Shut down your Mac, then turn it on and immediately hold down these four keys together:

Option, Command, P, and R.

Keep holding the keys for about 20 seconds, during which your Mac might appear to restart. (If you have a Mac that plays a startup sound when you turn it on, you can release the keys after the second startup sound.)

View hidden files and folders in OS X Finder

The following will display all hidden files and folders in Finder

  1. Open Terminal found in Finder > Applications > Utilities.
  2. In Terminal, paste the following: defaults write AppleShowAllFiles YES.
  3. Press return.
  4. Hold the ‘Option/alt’ key, then right click on the Finder icon in the dock and click Relaunch.

To reverse, repeat the above but substitute YES for NO at the end of the Terminal command.

OSX Instant Lock Screen

When leaving your Mac for a short time its a good idea to lock the machine.

To do this, first launch System Preferences and select Privacy and Security. Under the General tab select Require password immediately, close System Preferences. The following shortcuts will lock your machine.

Control+Shift+Eject is the keystroke for Macs with an Eject key, and for external keyboards.

Control+Shift+Power is the keystroke for Macs without the eject key, like the MacBook Air and MacBook Pro Retina.

Creating Symbolic Links OSX

The basic syntax for creating a symbolic link (or soft link) is as follows:

ln -s /path/to/original/ /path/to/link

For example, to create a symbolic link for the user Downloads folder which links it to a directory on a separate mounted drive, syntax may look like the following:

ln -s /Volumes/Storage/Downloads/ ~/Downloads/

That will link the active users ~/Downloads/ folder to a directory named “Downloads” on the mounted drive called “Storage”. If such a directory and drive existed, this would basically allow all files that would typically appear in the user downloads folder to go to the other mounted volume instead, essentially offloading the storage burden to that separate drive, while still preserving the appearance of a ~/Downloads/ folder for the user. As mentioned before, this behaves much like an alias.

Re-download OSX Lion

With the release of OSX Mountain Lion, Lion has been removed from the App Store. However if you’ve already purchased Lion it’s possible to download it again. Holding the option key while clicking Purchases in the App Store will make Lion reappear in the list.

How to check your Mac will run Mountain Lion

Apple have published details on which Macs can run Mountain Lion. However it is not always clear if your machine falls in to the specified categories. The following instructions allow you to run simple tests to check for comparability.

1. Open the About This Mac dialog from the main Apple menu and then click the More Info button to view the stats about your machine, including the model type. Also, look for Intel GMA 950 in the Graphics field. If present, then unfortunately your system is unable to run Mountain Lion.

2. The second way to confirm Mountain Lion compatibility is to click the System Report button and select the Software option. If the 64-bit Kernel and Extensions field reads “No,” your machine will not run Mountain Lion.

Finally, if you like the command line, run this command in Terminal:
ioreg -l -p IODeviceTree | grep firmware-abi

If the returned line says, “firmware-abi” =, you are out of luck – onlymachines will be Mountain Lion-ready.

Splitting DMG files into smaller segments

There are a number of tools which can split files, some free some not. However the versions I have tried seem rather hit or miss. Most people don’t relise that OSX can split DMG files without any 3rd party applications. You do however need to use Terminal (Applications > Utilities > Terminal) rather than an a pretty GUI.

The tool in question is called hdiutil, this allows you to attach, detach (eject), verify, mount, unmount and segment plus much more. Typing hdiutil help in to Terminal will display a help guide which is worth a look.

To segment a DMG file enter the following:

hdiutil segment -o mysplitimage -segmentSize 100M /Users/[your Mac username]/Desktop/myimage.dmg

This will create segments (mysplitimage.002.dmgpart, mysplitimage.003.dmgpart, etc.) in your Home folder of an image named myimage.dmg on your desktop.

-o specifies the name of the segments

100M specifies the segment size (K and KB can also be used)

It is also possible to specify the number of segments rather than size. Just replace -segmentSize with -segmentCount followed by the number.

It is not neccessary to rejoin the segments. Clicking the the first segment will mount the DMG in the same way as before the split.

OSX 10.7.2+ Guest Account on login screen

After installation of OSX 10.7.2 you may have found a ‘Guest User’ account at login.

This is not a full guest account. Clicking ‘Guest User’ will restart the Mac with a secure Safari only version of OSX. This has been added as part of the iClound ‘Find my Mac’ feature. This allows someone to ‘get you Mac online’ without access to your files. It is recommened this feature is left enabled, however it can be swiched off.

1. Open System Preferences
2. Click ‘Security & Privacy’
3. Click the lock in the lower left corner to allow admin access
4. Click ‘Advanced’
5. Check ‘Disable restarting to Safari when screen is locked’
6. Reboot

Creating a bootable OSX 10.7 Lion installtion USB drive

1. Download OSX 10.7 Lion from the App Store.
2. Navigate to the applications folder.
3. Right click on Install Mac OSX and select Show Package Contents
4. Open Contents directory and then SharedSupport
5. Double click InstallESD.dmg to mount the image.
6. Plug in your USB memory stick (must be at least 8 Gb)
7. Run Disk Utility
8. Select the USB drive from the left side of Disk Utility, click Erase tab.
9. Chose Mac OS Extended (Journaled) and enter a name.
10. Click Erase to format.
11. Once complete right click the USB drive in Disk Utility and select Restore
12. Drag the mounted InstallESD.dmg image from the left side in Disk Utility to Source.
13. Drag the USB drive from the left side in Disk Utility to Destination.
14. Double check the source and destination are correct and click Restore.
15. Once finished you will have an OSX 10.7 installation USB drive.