I wrote that I had experienced a panic at boot in El Capitan, and that I was hanging off reinstalling some software until I had found the problem.
I found the problem.
I had cause to reboot the system, and it hung again at the boot screen
So, I rebooted in Single User mode (Command-S) and this time I looked closely at the screen.
panic(cpu 0 caller 0xffffff80017d6a9a): Kernel trap at …
Debugger called: <panic>
Backtrace (CPU 0), Frame : Return Address
Kernel Extensions in backtrace:
A little research pointed to Eltima’s SyncMate, which I had installed to sync an Android phone. I had removed it some time ago, but it had left behind a kernel extension, which hangs El Capitan at boot (sometimes. But once it’s started, it doesn’t seem to stop)..
I completely removed the vestiges of SyncMate, by removing the files/folders:
- /Library/Application Support/EltimaSyncMate/
and all is now fixed.