Building a Base OS X Image

InternalHardDriveBuilding a base OS X image is very important for any IT administrator! In previous posts, I have talked about Imaging Workflows and When to Use Them and Creating a Bootable OS X Installer.  I also added a new post on Building and Deploying a OS X with AutoDMG. You will need about an hour or two, an empty partition, the OS X installer, and a tool to capture the finished product. The end result of this workflow will be a small base image that can be used in a modular imaging workflow. If you choose to do monolithic imaging, I would recommend that you follow this guide and save a copy of your image before installing additional software titles.

My Test Hardware and Software:

  • MacBook Pro 13″ (Early 2011)
  • OS X Mavericks (10.9)
  • Composer 9.32
For the purposes of taking quick screenshots during the Setup Assistant, I used Parallels Desktop to show the process. I would ONLY recommend using physical hardware when building a base image. Also, I do not cover build versions in this tutorial. If you do not have experience with builds or split-builds of OS X, please refer to Wikipedia and select the OS X version or go to Apple’s Support Page.

Part 1 – Install OS X

The first thing we need to do is to install OS X. You can use your bootable copy of OS X (that you built from my last post) and startup your Mac holding down the Option key. This will allow you to select your bootable drive. From there, you should see a screen similar to the one below.

Mavericks Install Welcome Screen

Once you are booted, select your language and then select Disk Utility on the next screen. Why Disk Utility? Well, it is because we don’t want a large partition for our base image. We will want to take advantage of Apple System Restore (ASR), and to do that the image must be the same size or smaller than it’s destination. I usually use a 20GB partition but anything smaller than your smallest drive will be fine.

Bonus Points: this process will be a lot faster if you use a SSD drive. When building my own images, I like to use an external drive. That way, it easy for me to move the image around and to capture with my workstation. I also don’t have worry about erasing anything when building a new image!

Once we have partitioned our drive accordingly, it is time to start the install process! Go ahead and go up to File and choose Quit. Next, select to install (or reinstall) OS X and proceed with the the legal stuff and selection of your partition. This part will vary greatly depending on the installer, your internet connection, and the hard drive you are using. For me, the install took about 45 minutes.

Part 2 – The Setup Assistant

Once you are finished installing OS X, your computer will reboot. The next thing we will have to configure is the Setup Assistant. The first few steps of this process are to choose your country, keyboard configuration, and network connection.

After that, we will be asked about data migration, configuring iCloud, and software agreements.

Up until now, much of this process has been: yes, yes, next, continue, skip… However, we have gotten to a very critical part, the first user account. In my workflows, I typically make this my desktop support user. This would be the account that my support staff know and can use for troubleshooting. Please note, that the first user created in OS X is an administrator.  Additionally, this page has checkboxes for screen unlock, time zone, and diagnostics.

Setup Assistant User Account

Lastly, we will be asked if we want to register the computer. When we click continue, the Setup Assistant will make these changes and will login as the user we created above.

Part 3 – Configuring OS X System Preferences

Next, we will to cover tweaks to System Preferences. While lots of theses things can be done via script, managed preferences, or configuration profiles; sometimes it is easier to do these things at this stage.

Start by going to Apple Menu and then to System Preferences. We will want to start in the Sharing pane and modify computer name, remote login, and remote management.  For the computer name, I typically throw in something like BaseImage.

Important note: you will usually change the computer name with your imaging tool. If not, a post imaging script to change your computer name is important.

As far as remote login and remote management, I like to have these on. While it is possible to manage computers with out these turned on, you will not have access to Apple Remote Desktop (ARD) or other potentially useful tools. If you do decide to turn on the remote settings, please make sure to set logins for specific groups or admin accounts and not everyone. This is mainly security reasons.

Once you have computer name and remote settings configured, click Show All and go into Users and Groups. Next, click the lock button on the bottom left and authenticate with your admin account. From here, you might want to turn on Name and Password instead of List of Users. Also, you can turn off things like: Fast User Switching, password hints, and Automatic Login. We will also want to select our Guest account and turn if off if we don’t need it.

After configuring Users and Settings, click Show All and go into App Store. In here, we will want to configure settings that work for us. In my environment, I am going to control the flow of updates with a Software Update Server. Since I’m going to control what my end users see and when the updates happen, I will uncheck all of these boxes. It would also be a good time to check for any patches an install them. I usually check for updates until I get two sequential checks that say no updates available.

The last preference pane to go into and configure is Date and Time. To do this, click the Show All button and then go into Date and Time. Next, ensure that that you are using the correct time server and that date and time are correct. If they are not, go over to Time Zone and verify that the proper closest city is selected and/or automatic time zone configuration is on.

At this point, I will usually shutdown my computer and take my external drive to my workstation. If you have additional things you wish to configure, please do so now and then start with part four when finished with your tweaks.

Part 4 – Capturing the Base Image

The last section of this tutorial will quickly show how to use Composer to capture the base image. There are other tools you can use but this is the one I prefer. More info about Composer can be found on JAMF Software’s website.

Start out by launching Composer, authenticating with your admin account, and clicking the New button on the navigation bar. This will bring up a screen that will allow you to choose what you are looking to build. Go under Operating System and select Build OS Package. You will see every partition, drive, and mounted disk image on your computer. Not everything that shows here is always a base image. Choose the right partition (this is why I like an external drive) and click next.

Please note that you cannot capture the partition you are booted from. This is because Composer has to unmount the drive for the file copying process.

Select Partition Composer

Next, we will need to choose what options we would like Composer to have when building our base image. I have rarely ever unselected any of these options. Most of these are in place to ensure that all unique data about the image is pulled and that possible management information is gone.

Composer Options

After you select your options, Composer will ask you were you would like to save the file and will start to copy the information as quickly as possible. Once Composer is finished, feel free to upload that file to your management solution and start imaging!

Composer Building Image

Additional Goodies

For folks that are in large organizations or have student workers build base images, I like to have checklists for them to follow.  To go along with this tutorial, I have build a Numbers Spreadsheet as well as a PDF that you can download. Feel free modify and use!

Numbers – Base Image Checklist

PDF – Base Image Checklist

4 thoughts on “Building a Base OS X Image”

  1. Hey Kyle,

    Great post, very informative.

    Personally, I’d rather go down the AutoDMG route, using scripts and packages to customise my images as needed. I find I’m even less likely to forget or miss a step then!

    Although I understand that there are a lot of Mac Admins out there that do not perhaps have the knowledge or even time to do it my way, and this is great for them!



    1. Hey Darren- I am happy that the info is helpful! AutoDMG will actually be my next topic (oops cat is out of the bag). I am hammering out a few scripts to go along with the post so that the outcomes are the same.

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