Payload-Free Package Creator.app Revisited

I do a lot of work with payload-free packages and while I have a process for creating them as I needed them with pkgbuild, this approach requires some setup work. To help make the package creation process more convenient, I developed Payload-Free Package Creator.app, an Automator application that will allow to select an existing script and create a payload-free package that runs the selected script.

However, this tool has used pkgbuild‘s –nopayload function, which creates a package which doesn’t leave an installer receipt behind. This is intended behavior according to Apple, but not leaving a receipt behind can make it hard to determine whether an installer package has been run on a particular machine. This is especially problematic for Munki, which uses receipts along with other methods to track installation status.

While I don’t use Munki, I’ve heard from a number of folks who do and who had run into the no-receipt problem when they tried to use payload-free packages generated by Payload-Free Package Creator.app with Munki.

So the problem was this:

1. I wanted to create payload-free packages which only run scripts and do not install files.
2. I wanted to have an installer receipt.
3. Apple’s built-in method for generating payload-free packages with pkgbuild didn’t provide receipts.
4. I thought I needed to provide a payload to pkgbuild in order to generate a package which would provide receipts.
5. Providing a payload meant I was installing files, which is what I didn’t want to do.

The matter had rested there for a while and I didn’t see a good way to fix it.

Fortunately, I was wrong about point 4. Greg Neagle recently documented that you can make a package with pkgbuild that, while not technically payload-free, will act just like one. The key is to create an empty directory and set pkgbuild‘s –root option to look there for files. pkgbuild‘s –root option is used to tell pkgbuild which files to package, but since there will be no files in an empty directory, the package will install no files on the destination Mac.

That’s where I had gone wrong on point 4 – I thought I had to give pkgbuild something to install in order to build a package with a receipt, but it turns out that pkgbuild will successfully build a package while using an empty payload directory. This information allowed me to reconcile points 1 and 2, which resolved the problem.

With this new information, I was able to update Payload-Free Package Creator.app and I’m happy to announce it has two new features:

• Version numbering
• Packages generated by Payload-Free Package Creator.app will leave receipts behind after installation.

For more details, see below the jump.

Using Payload-Free Package Creator.app

 

1. If needed, download the Payload-Free_Package_Creator_Application.zip file from the application directory in my GitHub repo.

2. Once downloaded and unzipped, double-click on the Payload-Free Package Creator application.

3. You’ll be prompted to select the script that you want to use as part of creating the installer package.

 

4. Once you’ve selected the script, you’ll be prompted to name the installer package. By default, the name filled in will be Payload Free Installer Package.

 

This name can be changed as desired.

 

5. Once you’ve entered a name for the installer package, you’ll be prompted for a package identifier. By default, the name filled in will be com.github.payload_free.

 

This name should be changed to be something unique.

 

6. Once you’ve entered an identifier for the installer package, you’ll be prompted for a version number. By default, the value filled in will be 1.0.

 

This value should be changed to be something unique.

 

7. Once the package name, package identifier and package version number have been set, Payload-Free Package Creator.app will prompt for an administrator’s username and password.

 

8. Once the admin username and password are provided, Payload-Free Package Creator.app will create the installer package and prompt you when it’s finished.

 

9. Click OK at the prompt and a new Finder window will open and display the newly-created installer package.

 

10. Payload-Free Package Creator.app will automatically exit.

 

How Payload-Free Package Creator.app works

Payload-Free Package Creator.app is an Automator application that uses AppleScript, shell scripting and pkgbuild behind the scenes to create installer packages which only run scripts but which will leave behind receipts. When a script is selected, the following process takes place:

1. The script is copied to /tmp and renamed to postinstall, to match the name that pkgbuild is expecting for a post-installation script.
2. After the package name, package identifier and package version number are chosen, /tmp is checked to make sure that there is not an existing directory that is named the same as the chosen name. If a matching directory is found, it is removed.
3. A new directory is created in /tmp that matches the chosen name of the package.
4. Next, a scripts directory and an empty directory named nopayload are created inside of /tmp/package_name_here. The nopayload directory provides the empty directory for pkgbuild‘s –root option.
5. The postinstall script is copied to /tmp/package_name_here/scripts
6. The package is built by pkgbuild using the postinstall script stored in /tmp/package_name_here/scripts
7. The finished package is stored in /tmp/package_name_here and the user is prompted that the process is finished.
8. Once the user is notified and clicks OK, a new Finder window opens for /tmp/package_name_here.

The AppleScript used to create the payload-free package as part of the Automator work is below:

	on run {input, parameters}
	— this repeat loop prevents empty strings from being submitted for the package name value
	set q to 0
	repeat while q is 0
	set result to text returned of (display dialog "Enter a Name For Your Payload-Free Installer Package:" default answer "Payload-Free Installer Package")
	if result is not "" then
	set pkgname to result
	set q to 1
	end if
	end repeat
	— this repeat loop prevents empty strings from being submitted for the package identifier value
	set q to 0
	repeat while q is 0
	set result to text returned of (display dialog "Enter a Package Identifier:" default answer "com.github.payload_free")
	if result is not "" then
	set pkgid to result
	set q to 1
	end if
	end repeat
	— this repeat loop prevents empty strings from being submitted for the version identifier value
	set q to 0
	repeat while q is 0
	set result to text returned of (display dialog "Enter a Version Identifier:" default answer "1.0")
	if result is not "" then
	set pkgvers to result
	set q to 1
	end if
	end repeat
	— Set the postinstall script to be executable
	do shell script "chmod a+x /tmp/postinstall" with administrator privileges
	— Remove any existing build directories that have the same name as the new payload-free package
	do shell script "rm -rf /tmp/" & quoted form of pkgname & "/" with administrator privileges
	— Create the build directories for the payload-free package
	do shell script "mkdir /tmp/" & quoted form of pkgname & "" with administrator privileges
	do shell script "mkdir /tmp/" & quoted form of pkgname & "/scripts" with administrator privileges
	do shell script "mkdir /tmp/" & quoted form of pkgname & "/nopayload" with administrator privileges
	— Move the postinstall script into the correct build directory
	do shell script "mv /tmp/postinstall /tmp/" & quoted form of pkgname & "/scripts" with administrator privileges
	— Build the payload-free package
	do shell script "pkgbuild –identifier " & quoted form of pkgid & " –version " & quoted form of pkgvers & " –root /tmp/" & quoted form of pkgname & "/nopayload –scripts /tmp/" & quoted form of pkgname & "/scripts /tmp/" & quoted form of pkgname & "/" & quoted form of pkgname & ".pkg" with administrator privileges
	— Display dialog that the payload-free package has been created
	display alert ((pkgname) as string) & ".pkg has been created."
	— Open a new Finder window that shows the new package
	do shell script "open /tmp/" & quoted form of pkgname & ""
	return input
	end run

view raw

gistfile1.applescript

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All Payload-Free Package Creator components and scripts are available at my GitHub repo:

https://github.com/rtrouton/Payload-Free-Package-Creator

The Automator workflow files and the AppleScript are also available via the link above if you want to build a customized Payload-Free Package Creator for your own environment.

 

An installer for the latest release of Payload-Free Package Creator.app is available via the link below:

https://github.com/rtrouton/Payload-Free-Package-Creator/releases/latest