init is the first (daemon) process spawned during the boot sequence of a UNIX system. It is initiated by the kernel, which will panic if the init executable cannot be found.

This process has some particular characteristics:

  • While there is no design rule behind this, the init process has PID 1, since it is the first child of process 0 (swapper or sched).
  • init adopts all orphan processes in the system.
  • init handles all operations related to programs starting at boot time. This behaviour can be configured through the /etc/rc* files and directories.

Further reading

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