Super User is a question and answer site for computer enthusiasts and power users. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

What is Difference between shutdown (power off) and restart (reboot) ?

  • What type of signals passing at time of reboot and poweroff, to where ?

  • What is difference between these two signals ?

At the time of reboot,

  • Is the operating system go to shutdown mode ?

  • If it goes shutdown, Which is make it to start again ?

Please correct it, if you find and mistakes in my questions

share|improve this question
up vote 5 down vote accepted

For the operating system, shutdown and reboot are practically the same thing.

The OS will shut down as usual in both cases. The only difference is the signal sent to the hardware at the very last moment.

To switch off/reboot the computer, the OS will send a special signal to the hardware once it is finished shutting down. It's only this signal which will be different between a reboot and a shutdown.

The way the signal is sent depends on the exact hardware platform. On modern systems it is usually done via ACPI.

share|improve this answer

Go to

share|improve this answer – Martin Oct 3 '11 at 17:35

The difference is that during reboot system is entering runlevel 6 and for shutdown it is runlevel 0.

It is similar to running

init <runlevel_number>

For more details on runlevels see

Under /etc/rc<runlevel_number>.d/ (e.g. /etc/rc6.d/) directories you will find script executed on entering specific runlevel.

share|improve this answer

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .