Two iMacs will not boot after the 10.11.4 update.
Two iMacs will not boot after the 10.11.4 update. Progress bar starts to move then text appears on the black screen saying unexpected sigkill of launchd. It then gets stuck in a loop of trying to boot. Tried resetting SMC and PRAM. No success. Booted into recovery mode and ran disk utility. Drives reported OK. Chose to reinstall OS X from the recovery mode option list (presume this would be 10.11.4). Install completed but again fails to boot. Reinstalled 10.11.0 successfully from a USB stick and downloaded the 10.11.4 combo updater. The installation appears to work but again the macs will not boot. Same "unexpected sigkill of launchd" error. One mac is now back working properly with 10.11.3 the other will be shortly. Is there a problem with the updaters? Our IT support use Munki to push out updates overnight. Thankfully we were able to stop this before the other 20 or so macs had the same problem.
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howapple - hello
I started that test after restoring to 10.11.3 but I had to cancel the test as it was taking more than 25 mins. We also had a response from another forum asking if we had SUIDGuardNG.kext installed.
We found that file on both restored iMacs but not on the test iMac that was successfully updated to 10.11.4 (It hadn't ever had 10.10 installed and so hadn't had the SUIDGuardNG.kext installed). I removed the kext file from one of the restored iMacs and then ran the 10.11.4 combo updater. It installed perfectly this time.
Check in /Library/Extensions.
Thanks for your help and hopefully this will solve the issue for others.