"shutdown now" on F11 as root problems and app crashes in

Rick Stevens ricks at nerd.com
Mon Nov 2 22:05:41 UTC 2009

Phil Meyer wrote:
> On 11/02/2009 11:39 AM, KC8LDO wrote:
>> Rick;
>> I just checked the command line version, using "--help", as you 
>> suggested, and the info is there, of course. I wasn't expecting that 
>> sort of default behavior. Nothing in the man page that warns about it. 
>> Somebody may want to consider adding that tid-bit to the man page. I 
>> thought the man pages were the main source of info for various 
>> commands etc., looks like it isn't. Guess I'll just have to be more 
>> careful. Another day, learn something new.
>> Thanks;
>> Leland C. Scott
>> ----- Original Message ----- From: "Rick Stevens" <ricks at nerd.com>
>> To: "KC8LDO" <kc8ldo at arrl.net>; "Community assistance, encouragement, 
>> and advice for using Fedora." <fedora-list at redhat.com>
>> Sent: Monday, November 02, 2009 1:19 PM
>> Subject: Re: "shutdown now" on F11 as root problems and app crashes in
>>> KC8LDO wrote:
>>>> Bob;
>>>> I did go back and read it, should have done that first. I did read 
>>>> that one of the options the action taken is system dependent, the 
>>>> "-h" option. That makes things more interesting.
>>>> I'm sitting here at work, eating lunch, reading the man page, again, 
>>>> for the shutdown command using a remote VNC session to my F10 box at 
>>>> home. I don't see anything that mentions any sort of default action 
>>>> if you fail to supply one of the options to the shutdown command. 
>>>> All it says in general at the end of the man page is :
>>>> "When invoked it generates a runlevel event, with an argument 
>>>> containing the new runlevel."
>>>> I'll have to look specifically at the one, man page, on the F11 box 
>>>> later when I get home. Your comment suggests they are not the same.
>>>> One last comment. If I was not by the local attached console and saw 
>>>> what happened, but was working remotely when I issued the "shutdown 
>>>> now" command, having the system drop down to a CLI interface, single 
>>>> user mode, with the root prompt showing isn't very comforting. Also 
>>>> my remote VNC session terminated too. Not my idea of a way to lose 
>>>> control of the box and give somebody else the chance to have some 
>>>> fun at the "free" root prompt either. Lucky for me this box is on my 
>>>> home network where I'm the only one with physical access.
>>> "shutdown --help" on both F10 and F11 result in this data:
>>> "<snip>
>>> The system is brought down into maintenance (single-user) mode by
>>> default, you can change this with either the -r or -h option which
>>> specify a reboot or system halt respectively.  The -h option can be
>>> further modified with -H or -P to specify whether to halt the system, or
>>> to power it off afterwards.  The default is left up to the shutdown
>>> scripts.
>>> </snip>"
>>> So it goes to run level 1 or "s" by default.
> Just to add confusion to your research, you will find a whole group of 
> UNIX/Linux admins that prefer to use the init command to shut down or 
> change the state of a system.
> These admins, like myself, are SYSV oriented, where the shutdown command 
> was a simple shell script that called the init program.
> On Fedora, SUSE and other SYSV oriented Linux distros, the old habit of 
> using init is supported.
> Thus:
> # init 0
> Goes to power off mode in Linux, and to firmware mode on Solaris.
> # init 3
> Goes to run level 3.
> # init 5
> Goes to run level 5, except on Solaris, where it is power off! :)
> # init 6
> Is the equivalent of typing reboot.

I, too, am an old SVR4 guy.  However, I never used the init commands
directly unless something dire was going on.  Certainly not "init 0"
or "init 1" because you could corrupt filesystems like that.

At the VERY least, you should run "sync" once or twice to make sure the
disk buffers were flushed, e.g. "sync;sync;init 1".  The shutdown
command at least blocks new logins, sends SIGHUP and SIGTERM signals to
processes and syncs the disk before doing anything drastic.

telinit does similar things unless you use the "S" or "s" options (which
do the old "drop to run level 1 immediately" thing complete with
potential filesystem damage.  Unless you know what you're doing, stay
away from the init command.
- Rick Stevens, Systems Engineer                      ricks at nerd.com -
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