Creating (and restoring) an image in OS X: El Capitan
August 25, 2018
The idea of an image is a wonderful thing, especially if you have a team of more than few folks. Images allow you to standardize the setup and configuration of your OS so that everyone on your team is more or less running the same thing. El Capitan changed the way images are created (and restored) and it gave the team a bit of hell this past week. To hopefully help you avoid some of the same perils, here are step-by-step instructions on how to create an image and then use that image to setup a new computer.
Image Creation
Thankfully setting up a new image isn't terribly challenging.
Open Disk Utility
File -> New Image -> Image From Folder
If you want the entire OS, config, and applications, select the entire HDD (or SDD, whatever it may be). Click Done.
This will create an image (with extension .dmg)
Restoring the Image
Now this is the part that gave me hell. I wanted to wipe my hard drive clean and start with a fresh install. I put the .dmg (the image) on a flash drive and tried to restore. However, I kept receiving a really generic error saying the file could not be scanned. My image was ~9 GB. My flash drive was ~15 GB. So I had no idea what the issue was. (<-- bolded and emphasized because this is the one thing that haunted me for days) After days of digging, I finally found a helpful command within disk utility called "Scan Image for Restore". When you run this, get a beer and go watch an episode of Breaking Bad b/c it took about an hour for it to finish. Running this command informed me that my flash drive was too small. I have yet to find documentation that says how much room you need but I can tell you that changing to a flash drive that was approximately 3 times larger than my image file did the trick.
The other gotcha is that the actual restore sequence is a little confusing to me. After trial and error, I sorted it out. Instructions for restoring are below.
Reboot your computer. As soon as the computer flashes back on, hold CMD + R. This boots into recovery mode.
Select Disk Utility
Select the disk you want to restore to. In this case I selected "OS X" under "Internal"
Go to Edit --> Restore
Select the image you want to restore from (the image you created above). In this case I selected what we call our "Standard Image" (we're clever as hell when it comes to naming stuff)
Click restore. Your computer will now update your computer w/ the image file you created
Reboot
And you should now be good to go. Enjoy your newly refurbished OS!
