What is the difference between the shutdown, halt and reboot commands?

Question

Should I be using one or the other for different things?

Solution

halt brings the system down to its lowest state, but leaves it powered on.

shutdown brings the system down to its lowest state, and will turn off power (soft power switch) if it can. Most computers now can do so.

reboot restarts the system. It brings the system down to its lowest state, then starts it up again.

Which to do depends on what you want to do. halt is usually to get to a state where you can perform low level maintenance. shutdown is to power the system off, and reboot is to reboot it.

Comments

[Admin]

man halt covers the differences

[Wuffers]

Whenever I use the halt command on Mac OS X and Linux, it completely shuts my system down.

[Thom G]

This is slightly incorrect. shutdown can bring the system to any of these states, including single user mode (the default). Also, there is the poweroff command, turning power off (if possible).

[loosecannon]

yeah halt also completely turns my computer off ( Ubuntu server 9.04) but I normally just type halt to poweroff and reboot to restart because its shorter than the shutdown command. Any harm in that?

[Greenonline]

@loosecanon - ask your question in a separate question. :-) There is actually an issue with what you suggest, and could cause data loss.

[Manuel Jordan]

@RichHomolka about "halt is usually to get to a state where you can perform low level maintenance" what do you mean with that?. Thanks

[Rich Homolka]

@ManuelJordan it’s not really used anymore, it was used back in the days of big honkin’ Solaris boxes. It was used to get the machine where the OS wasn’t running, whether that meant power off or drop to the equivalent of bios or whatever.

[Manuel Jordan]

@RichHomolka thanks for the polite explanation.