Shutdown -h vs. Poweroff / Shutdown -r vs. Reboot

[aab45]

Does anyone know what the differences are between these commands?

shutdown -r vs. reboot

shutdown -h vs. poweroff

I know that poweroff actually turns off power to the system while 'shutdown -h' does not.

Are there any other differences between the above commands?

[jtang613]

The reboot and poweroff commands in the /usr/bin directory are symbolic links to /usr/bin/consolehelper. These are the default commands for normal users.

Originally Posted by consolehelper manpage

consolehelper is a tool that makes it easy for console users to run
system programs, doing authentication via PAM (which can be set up to
trust all console users or to ask for a password at the system adminis-
trator’s discretion). When possible, the authentication is done graph-
ically; otherwise, it is done within the text console from which con-
solehelper was started.

It is intended to be completely transparent. This means that the user
will never run the consolehelper program directly. Instead, programs
like /sbin/shutdown are paired with a link from /usr/bin/shutdown to
/usr/bin/consolehelper. Then when non-root users (specifically, users
without /sbin in their path, or /sbin after /usr/bin) call the "shut-
down" program, consolehelper will be invoked to authenticate the action
and then invoke /sbin/shutdown. (consolehelper itself has no priv-
iledges; it calls the userhelper(8) program do the real work.)

consolehelper requires that a PAM configuration for every managed pro-
gram exist. So to make /sbin/foo or /usr/sbin/foo managed, you need to
create a link from /usr/bin/foo to /usr/bin/consolehelper and create
the file /etc/pam.d/foo, normally using the pam_console(8) PAM module.

The root user, by default, executes those commands from /sbin. The poweroff and reboot commands in /sbin are symbolic links to the 'halt' executable. Which itself is really just a wrapper for the 'shutdown program.

Originally Posted by halt manpage

Halt notes that the system is being brought down in the file
/var/log/wtmp, and then either tells the kernel to halt, reboot or
poweroff the system.

If halt or reboot is called when the system is not in runlevel 0 or 6,
in other words when it’s running normally, shutdown will be invoked
instead (with the -h or -r flag). For more info see the shutdown(8)
manpage.

All this tangled mess is setup to allow normal users (with proper permission) to poweroff or reboot the system without being root.

hth,
Jason