In the not-too-distant past, OS X system patches were rather innocuous and straightforward and I gave very little thought when I initiated the installation. These days, incremental updates (e.g., upgrading from ‘dot-one’ to ‘dot-two’) that typically take up one or two gigabytes of disk space affect key components of the Mac’s operating system in a variety of ways and, thus, can have a greater chance of wreaking havoc.
I’ve found this to be the case with the last two El Capitan updates: 10.11.3 and 10.11.4. In both instances, the download and installation process completed fine, but when I tried to log into my admin account, the system immediately froze and I was left to stare at a spinning beach ball on my screen that would not go away.
As an IT professional, I am well aware of the importance and necessity of having one or more reliable backups. Before attempting both of these OS updates (10.11.3 a few weeks ago and 10.11.4 yesterday), I cloned my boot drive using SuperDuper 2.8. As an alternative, I could have backed up my computer using Time Machine or Carbon Copy Cloner.
Having dealt with a variety of issues on both Macs and Windows PCs, I came up with the following strategy that fixed the 10.11.4 installation problem:
1. I booted up from my cloned drive that was configured with 10.11.3. Using SuperDuper, I restored the contents of my boot drive back to 10.11.3. Afterward, I started up my Mac in a normal manner.
2. I temporarily disabled Avast Mac Security 2015, my anti-virus software. Many Windows installers advise users to disable their AV programs prior to starting a software installation, so I figured that this technique might be useful on my Mac.
3. An Internet search revealed that a system extension that is used by HP printers could be problematic with El Capitan. I don’t own any HP printers, so I opened a Terminal session and entered this Unix command to move the HP printer extension to my desktop:
sudo mv /Library/Extensions/hp_io_enabler_compound.kext ~/Desktop/hp_io_enabler_compound.kext
To execute the sudo (superuser do) command, I entered my admin password in the popup window. If you are operate an HP printer on a Mac, pay attention to note #6 below.
4. I manually downloaded the incremental 10.11.4 installer from Apple’s website and used that as my upgrade source, rather than the installer available from the App Store. As an alternative, I could have chosen to download the 10.11.4 combo, but chose the incremental version to save on disk space.
5. After my Mac rebooted into 10.11.4 and I was able to authenticate to my desktop screen using my user account and password, I re-enabled my anti-virus software, Avast.
6. I opened another Terminal session and executed this command to move the hp_io extension back to its original location:
sudo mv ~/Desktop/hp_io_enabler_compound.kext /Library/Extensions/hp_io_enabler_compound.kext
Since I don’t have a need for this system extension, I could have deleted it from my Mac without causing any problems. If you receive an error that your HP printer driver was installed improperly and cannot be used after performing the above steps, that is likely the result of a file permission conflict. The kext file needs to be ‘owned’ by the system (aka root), and if it is simply copied by the user to his or her desktop, the ownership changes to that person’s account.
If the kext file permission is set incorrectly, a quick way to fix it is to execute the chown (change owner) command from Terminal:
sudo chown -R system:wheel /Library/Extensions/hp_io_enabler_compound.kext
Because the kext file consists of multiple files and folders nested together into a single document, execute the chown command using the Recursive (-R) flag option. Again, because you’re executing this Unix command as SuperUser, you would also need to enter your admin password when prompted.
In the unlikely event that changing the permissions of your hp kext file prevents your printer from working after installing 10.11.4, your backup source would be the printer software that’s downloadable from HP’s website. Chances are, however, that OS X includes the most current HP printer driver that’s supported by your operating system.
If you run into a login problem that transpires from an El Capitan 10.11 incremental installation, you are welcome to try this technique to see if it helps. However, because of the wide variety of configuration variables (both hardware and software) to consider with every Mac, I offer no guarantee of success and encourage you to proceed with caution, every step of the way. Good luck!
El Capitan Kernel Extension List
Apple Developer Forums
Oct 2, 2015
OS X 10.11.4 El Capitan Update Available to Download
Mar 21, 2016
8600e Printer driver Improper installation of hp_io_enabler_compound.kext
HP Support Forums
July 25, 2015