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In Linux, the init 6 command gracefully reboots the system running all the K* shutdown scripts first, before rebooting. The reboot command does a very quick reboot. It doesn’t execute any kill scripts, but just unmounts filesystems and restarts the system. The reboot command is more forceful.

Source: http://www.vreference.com/2009/09/23/reboot-is-not-the-same-as-init-6/

This seems to be true for Unix systems as Solaris, but I have always seen the following 3 commands as synonyms, as they all seem to shut down the services before unmounting the filesystems and restart the server:

shutdown -r now
reboot
init 6

Can somebody tell the differences between these commands?

ujjain
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1 Answers1

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There is no difference in them. Internally they do exactly the same thing:

 1. reboot uses the shutdown command (with the -r switch). The shutdown command used to 
    kill all the running processes, unmount all the file systems and finally tells the
    kernel to issue the ACPI power command.

 2.init 6 tells the init process to shutdown all of the spawned processes/daemons as
   written in the init files (in the inverse order they started) and lastly invoke the 
   shutdown -r now command to reboot the machine
Abhishek Anand Amralkar
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  • Wish you mentioned, the source of above copied content from [here](https://unix.stackexchange.com/questions/64280/what-is-the-difference-between-reboot-init-6-and-shutdown-r-now) – harshavmb Mar 15 '22 at 16:26
  • That is not the same. Init 6 will run all the relevant shutdown scripts for the services. reboot may or may not do this depending on the OS and distribution. (generally safe on modern linux machines) Killing process vs running shutdowns my leave certain apps in an inconstant state, which may prevent restart on the next boot. Especially if a kill -9 is used. Just a warning from a seasoned unix bod – krad Mar 21 '22 at 11:45