Strange boot issue


Hello again folks. I'm having a strange problem on a large chunk of our High Sierra and Mojave Macs, and wondered if anybody else had seen anything similar. I'm still a relative newbie at troubleshooting this stuff, so apologies if any pertinent details are missing...

What I'm finding at the moment is that virtually our entire fleet of Macs (whether High Sierra or Mojave) are hanging during some reboots, with the loading bar stopped at various points. While in this state, if I hold the power button down and power them off and back on again, they'll boot fine and continue to work until some point during the next few days another restart is triggered, then they'll hang again until I physically power them down and back on. The system doesn't hang if I trigger a restart direct from the OS or via a terminal command, or after a shutdown.

Has anybody else seen anything similar? On poking through the logs on one that has frozen, I can see the Jamf agent running an immediate reboot command following whichever policy has triggered it, but then nothing after that until the system comes back up again following manual intervention, which may suggest the problem is related to Jamf-triggered reboots? (I'm on Jamf version 10.11.0 if that's significant)

Is the best step to troubleshoot this to create a self-service policy to trigger a restart, then try and capture a verbose boot?

Thanks in advance for any suggestions!



@MBrownUoG Might be worth trying a PRAM reset (hold command/option/P/R during boot). You should see the screen flicker 3-4 times, then release the buttons and let the machine boot normally. If you have older Macs that chime during boot, let it chime 3-4 times.

Other thing that might help is a SMC reset (hold shift/control/option) during boot

Contributor II

I had this problem with 1 set of iMacs in our lab. They would boot and then hang at the full loading bar for multiple hours and never progress further. The solution was to unplug them from power (not just turn them off) and leave it unplugged for about 30s, so the SMC can reset. I tried Recovery mode, Verbose modes, resetting PRAM, but it was the SMC.


Thanks both. I’ll try that tomorrow.

New Contributor

Am Jamf Connect user only, so not using Pro as MDM.
We are seeing some Macs getting stuck after Filevault login and
before login prompt appears (have disabled FV autologin).
Seeing several machines with this.
as you mentioned, power cycling them gets them through hiccup
but it reoccurs randomly it seems.