I'm trying to format and fresh install all macs here at our school using netinstall. As we were already having this issue with our previous server installation, I got a new machine and setup the server from scratch, deploying server.app, reissuing certificates, reconnecting it to our apple school manager, and so on. I created brand new el capitan netinstall images from a fresh mac app store download and system image utility [one default one, one custom with pre-emptive partitioning of the target drive via automator], activated netinstall on the server, and tried using netinstall on several macbooks and mac minis, with the same results as before: the installation almost always fails with "failed to extract essentials.pkg" after some time the progress bar is stuck at 17 minutes left. The server and clients are all on a wired lan on the same subnet, also tried isolating them and connecting them directly via ethernet with the server providing dhcp and the client happily netbooting, but with the same installation failure. The exact same copy of el capitan i used to create the image works perfectly if cloned to a usb key and installed manually directly on the client the classical way. The copy has the same checksum as another one i have on another mac so it's not a download failure. I tried both the n key press on boot method and the alt key on boot plus selection method. The custom image also blesses the netboot server [which is on a static ip on the network of course] but that doesn't help. Both images fail. Sometimes the clients don't even show the essentials.pkg error and simply reboot to their now-inexistent local filesystem. A few rare successes seem to occur immediately after the server is rebooted, and fail almost always after that. The same clients, throughout multiple trials, can show both error symptoms as well as successes, with errors occuring 95% of the time.
I'll try to add some client log messages from an actual installation. Server logs show nothing relevant.
If you have any helpful tips, please advise.
Thank you
