Mac Administration with Jamf, Part 5: Composer Package Scripts

As I mentioned in my last post in the "Mac Administration with Jamf" series, Composer not only allows you to package applications for deployment by including files and folders, but also gives you the ability to run scripts at certain points in the install process to achieve various things. 

This only works with .pkg-based installs - .dmg installers don't include any scripts, so if you want to do work other than copying files and folders, you will need to create a .pkg installer. Unfortunately, this also means that installers that use package scripts cannot be indexed and made uninstallable by Jamf, so you will need to create uninstallers yourself if they are needed.

According to the Jamf documentation for Composer, there are a number of triggers for which you can enter scripts. Rich Trouton, on his blog Der Flounder, explains when each of these triggers actually occur, and what can be done with each:

• Preflight - runs before any files are installed
• Preinstall - runs before files are installed, but after preflight, and only if this package has never been installed before
• Preupgrade - runs before files are installed, but after preflight, and only if this package (or an earlier version) has already been installed on the system
• Postinstall - runs after all files are installed, only if this package has never been installed before
• Postupgrade - runs after all files are installed, only if this package (or an earlier version) has already been installed on the system
• Postflight - runs after all files have been installed, and after other postinstallation tasks have occurred

At any stage, if the script does not return with an exit status of zero, Installer will display a message that the installation was not successful, and will exit.

With the new flat-package format for installers, only two of the above triggers are available: preinstall and postinstall. This means that the installer will not automatically detect whether an older version of the package has been installed, so you will need to do any such checks manually.

To add a script to a package in Composer, click the triangle next to the package source name to expand its subfolders. Right-click on the subfolder labelled Scripts, then hover over Add Shell Script (unless you prefer Perl), and select the type of script you wish to add. For this example, I'm adding a postinstall script.

Click on the newly-created script name, and you will be given an editor window into which you can type your script. Enter your script, or copy-and-paste an existing script, then save it with Cmd-S or File > Save. In this screenshot, you can see a script that we use to automatically download, install, and customize the latest version of Google Chrome, which frees us from the need to manually download and package each and every new version as it is released. I will discuss more details about this package, as well as those for Firefox and Adobe Flash Player, in future posts.

Once your scripts are created, build the package as a .pkg installer, and upload and deploy using Jamf like normal. Now, when Jamf runs the installer package, any scripts you entered will run at the appropriate times during the install.