Revisiting receipts for OS X installs via Munki

Background

When using Munki to upgrade OS X with a package created using createOSXinstallPkg (https://github.com/munki/createOSXinstallPkg), the recommendation has been to change the auto-generated receipts array:

https://github.com/munki/munki/wiki/Installing%20OS%20X#receipts

The intention here was to provide something that would satisfy Munki’s check to see if an item needs to be installed: if the recommended receipt is present, Munki won’t attempt to (re-)install the package that installs OS X.

A problem

However, I recently discovered an issue with this approach. For some machines here, an “InstallYosemite” item was added to their manifest’s managed_installs some time ago to force an upgrade to Yosemite. Once that upgrade was complete, the normal installcheck mechanism found a receipt for “com.apple.pkg.BaseSystemBinaries” of version “10.10.0.1.1.1412852630” or higher, and did not offer to reinstall Yosemite, even though the item remained in “managed_installs” in that machine’s manifest.

Later we added “InstallElCapitan” as an optional_install for all users (in an included_manifest). If a user with a machine manifest like the one described above then chose to self-upgrade to El Capitan, as part of the El Capitan install, the “com.apple.pkg.BaseSystemBinaries” receipt is removed. (Note that at https://github.com/munki/munki/wiki/Installing-OS-X/17e17bfdc80727bbd83595359eec6db2741fe88c, the previous recommended receipt to check for El Capitan is “com.apple.pkg.Essentials” since the “com.apple.pkg.BaseSystemBinaries” is not present in an El Capitan install.)

Once the El Capitan upgrade is complete, when Munki later checks for updates, it encounters “InstallYosemite” in the managed_installs. Since the “com.apple.pkg.BaseSystemBinaries” receipt is no longer present, it decides it needs to install Yosemite once again. This of course, fails, since the package itself has an installcheck, which errors with:


Cannot install on volume / because it is disabled.
-------------------------------------------------------------------------
installer: Cannot install on volume / because it is disabled.
installer: You can’t upgrade this version of OS X because a newer version
is installed.
-------------------------------------------------------------------------

If your InstallElCapitan package also includes the Munki bootstrap flag (to ensure all other needed updates for El Capitan are performed), this can lead to a loop where Munki attempts to install Yosemite, fails, tries again, etc.

A fix

The obvious fix is to remove “InstallYosemite” from all manifests once you are offering “InstallElCapitan”. But I think I have a way to avoid this situation in the future. I will recommend a different installation check item for createOSXinstallPkg-type items.

Instead of modifying the auto-generated receipts array, I will now recommend adding an installs array. Here’s one for El Capitan:


<key>installs</key>
<array>
  <dict>
    <key>ProductVersion</key>
    <string>10.11.4</string>
    <key>path</key>
    <string>/System/Library/CoreServices/SystemVersion.plist</string>
    <key>type</key>
    <string>plist</string>
    <key>version_comparison_key</key>
    <string>ProductVersion</string>
  </dict>
</array>

This directs Munki to look at the ProductVersion key in /System/Library/CoreServices/SystemVersion.plist, and compare it with 10.11.4. (you could even just make it “10.11” to prevent Munki offering this as an upgrade to 10.11.[0-3] machines.)

/System/Library/CoreServices/SystemVersion.plist exists in all versions of OS X, so it’s a better comparison than package receipts that may or may not exist in future versions of OS X. And it’s easier to revise in the future since the ProductVersion maps to the OS X version you are installing.

Revisiting receipts for OS X installs via Munki