from the shutdown(8) manpage:

A lot of users forget to give the time argument and are then puzzled by the error message shutdown produces. The time argument is mandatory; in 90 percent of all cases this argument will be the word now.

init 6 does the same thing

hi
when i try to install mandrake 10 it says'you may safely reboot or halt your system'.what is this???

This is just telling you it is okay to reboot or shutdown your system after the install. Most OS installations aren't complete until you've rebooted the system. Follow the instructions in this recipe to reboot and you should have a shiny new Linux box.

Most Distros also have an alias which you can type instead:

reboot

<ul id="quote">Most Distros also have an alias which you can type instead:

reboot</ul>

That is true. On Slackware Linux, both "halt" and "reboot" work. I know this is also true for OpenBSD.

If you'd like a user to be able to shutdown or reboot a machine, the easiest way to do this is through "sudo".

Other than Slack...n openBSD, the reboot and halt are supported by SuSE, Red Hat as well.

Reboot and halt DO NOT SAFELY shutdown a system. reboot is a symlink to halt and halt nukes the platform.

shutdown -rn now is how I usually reboot a machine of mine. shutdown -r by it's self will sync the disks, -n forces this (I like to be on the safe side).

halt just stops the processors and inits the system without syncing disks. You'll more than likely come back with your system running FSCK on your FS, and you better pray your using ext3.

Halt does NOT nuke a system

If the system is not in run level 0 or 6 halt/reboot/poweroff calls shutdown

so halt is really just a wrapper for shutdown

don't believe me? man halt

<ul id="quote"><h6>Anonymous wrote:</h6>Reboot and halt DO NOT SAFELY shutdown a system. reboot is a symlink to halt and halt nukes the platform.

shutdown -rn now is how I usually reboot a machine of mine. shutdown -r by it's self will sync the disks, -n forces this (I like to be on the safe side).

halt just stops the processors and inits the system without syncing disks. You'll more than likely come back with your system running FSCK on your FS, and you better pray your using ext3.</ul>

What type of idiot response is this. Have you ever heard of checking argv[0], it tells you how the process was called. Halt checks this and then runs according to how it was called.

if ((progname = strrchr(argv[0], '/')) != NULL)
progname++;
else
progname = argv[0];

if (!strcmp(progname, "reboot")) do_reboot = 1;
if (!strcmp(progname, "poweroff")) do_poweroff = 1;



Moral of this story "think before you open your mouth"