Replacement developer certificates Apple issued to fix security issues have caused signed packages created using the older replaced certificates to no longer be verifiable. This results in OS X assuming corruption in these files, and will not process them by default. One unfortunate side-effect of this is that older installers you may have collected for past versions of OS X will likely have been signed using older certificates, and may no longer install.
The solution to this is to simply re-download newer versions of current OS X installers from the App Store; however, many versions of OS X that people still use in virtual machines or on older Mac hardware may not be available, or may not have been re-issued with the proper certificates.
- Click “Cancel” on any current installation warnings
- At the OS X tools window, choose Terminal from the Utilities menu
- Enter the following command:
- Quit the Terminal and resume installing OS X
The “date” command here will set the date to January 1st, 2016, 1:01am. To use a different date, the values are in ordered pairs, where the first two represent month, followed by day, hour, minute, and finally year.
After the installation finishes, OS X will use time servers to automatically adjust the time, or you can again manually adjust the time in the Date & Time system preferences.
Finally, this issue may largely affect those who deploy many older systems for organizations and businesses. Therefore, be sure you create an updated set of system images for restoration purposes, in order to avoid having to use this workaround with the OS X installer. You can do so a number of different ways; however, the most vanilla approach is to wipe a system and install OS X freshly on it, followed by creating a clone of it to an external hard drive. You can also put the system into Target Disk mode, and then use Apple’s system imaging utility or Disk Utility on another Mac to create a restorable or bootable image of the system.