Re: [gentoo-user] Re: Emergency shutdown, how to?

[Steven Lembark]

Iain Buchanan wrote:
> On Sat, 2008-04-05 at 12:42 -0400, Steven Lembark wrote:
>>> I tried ALT + SysRq + EISUB today on my MythTV backend server which
>>> has been crashing lately. Unfortunately it's crashing so badly that
>>> even at the server's keyboard this didn't work.
>>>
>>> I guess my weekend fate of building a new server is sealed...
>> Have fun.
>>
>> Check out motherboards with watchdog capability
>> and enable it in the kernel.
>
> watchdogs are nice, and linux makes them ultra-easy to program, but of
> course if your watchdog task dies, then the machine effectively hits the
> reset button for you - no nice shutdown whatsoever!  (Which is what you
> want in a hard lock-up, but not if your programming skills are the cause
> of the problem :)

- Have the system turn off the watchdog if the file is
  closed.

- After that just open it and poke a bit out now and
  then.

- Make a point of closing the file on exit.

    #!/usr/bin/perl

    use strict;

    open my $fh, '<', '/path/to/watchdog/file'
    or die "Failed opening watchdog file: $!";

    # watchdog is now watching...

    select $fh;

    for(;;)
    {
        print "\n";

        sleep 1;    # watchdog timeout / 2
    }

    my $graceful_exit
    = sub
    {
        close $fh;

        exit 0
    };

    for sig in ( qw( TERM QUIT INT __DIE__ ) )
    {
        $SIG{ $sig }    = $graceful_exit;
    }

    for sig in ( qw( HUP ) )
    {
        $SIG{ $SIG }    = 'IGNORE';
    }

    __END__

-- 
Steven Lembark                                            85-09 90th St.
Workhorse Computing                                 Woodhaven, NY, 11421
lembark@×××××××.com                                      [phone]
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