Comments on: reboot is not the same as init 6 (updated)

By: Forbes Guthrie

Forbes Guthrie — Sat, 07 Nov 2009 17:44:12 +0000

Hi jsd,
last -x searches though the /var/log/wtmp and cats out all the entries related to run-level changes. So the whole command should tell you when the server was last shutdown or reboot. (I’ve corrected the showdown typo )

By: jsd

jsd — Sat, 07 Nov 2009 16:14:24 +0000

Folks…good thread…what exactly does last -x | grep -e showdown -e reboot do?

By: Marlena

Marlena — Fri, 09 Oct 2009 21:54:02 +0000

init 6 and shutdown -r does the same thing from the unix/linux standpoint. It is not harmful to use those 2 commands at all. It gracefully restarts the linux/unix system. Sometime it is also good to do a sync command to flush the cache buffers right before running these commands.

By: Forbes Guthrie

Forbes Guthrie — Fri, 25 Sep 2009 17:59:24 +0000

Hi Bert,
Thanks for the info. I’m happy to put my hand up when I’m wrong, so I’ll edit the page. You’re making me feel old
I guess I’ll still use the shutdown command, as at least I know where I stand.

By: Bert

Bert — Fri, 25 Sep 2009 10:31:04 +0000

Actually, the “older sysvinit releases” referenced in the man page are _much_ older than ESX 3. The Service Console in ESX 3 is a close relative of RHEL3. On RHEL3 (and ESX3) you have SysVinit 2.85, on RHEL5 (as on ESX4) you have SysVinit 2.86. The change happened long before that: version 2.54, in january 1995 (cfr /usr/share/doc/SysVinit*/ChangeLog

The reason not many ESX admins realize the “danger” of running reboot is that they use systems (like ESX) that aren’t that old, and that have the “safe” behaviour that we’ve known for more than 10 years now: reboot, init 0/6, halt, poweroff, and shutdown all cleanly shut down the system. Only caveat is: don’t add unnecessary options like -f or -n: those _are_ dangerous !.

cheers,
Bert.

By: Forbes Guthrie

Forbes Guthrie — Thu, 24 Sep 2009 04:31:28 +0000

Hi Andrew,
I agree things are changing. A lot of the latest versions of distributions symlink reboot to shutdown -r (presumably for the reason I stated above). Also Debian is moving to Upstart (from the older init system), so all the old commands are just links to replicate the functionality.
I’m fairly sure the advice is valid for the ESX 3.0 and 3.5 Service Console. Can anyone tell us how this is set on ESX 4.0 hosts?

By: Andrew

Andrew — Thu, 24 Sep 2009 02:52:44 +0000

That has not been my experience in Debian and CentOS. The following is the same on both Debian Unstable (sid) and CentOS 5.3

# which reboot
/sbin/reboot

# file /sbin/reboot
/sbin/reboot: symbolic link to `halt’

When you “man halt” (or “man reboot”), you will find the following paragraph in both distributions:

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.