Some hotkeys to hold when powering on the Mac:

  • +V --- Verbose mode
  • +S --- Single-user mode
  • --- Safe mode
  • --- Startup manager (select boot medium)
  • C --- Boot from CD-/DVD-ROM or USB
  • D --- Boot to diagnostics
  • +D --- Boot to diagnostics over the Internet
  • N --- Netboot
  • +N --- Netboot using default image
  • +R --- Boot to recovery
  • ++R --- Boot to recovery over the Internet
  • ++P+R --- Reset NVRAM
  • T --- Startup in target disk mode (to receive files from another Mac)
  • X --- Force boot to MacOS