linux-kernel - Re: signal to PID 1 from serial console like KeyboardRequest or CAD

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Message-ID: <20110401053757.GA9866@core.coreip.homeip.net>
Date:	Thu, 31 Mar 2011 22:37:57 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Randy Dunlap <rdunlap@...otime.net>
Cc:	Jeremy Jackson <jerj@...lanar.net>, linux-kernel@...r.kernel.org
Subject: Re: signal to PID 1 from serial console like KeyboardRequest or CAD

On Thu, Mar 31, 2011 at 12:57:06PM -0700, Randy Dunlap wrote:
> On Fri, 25 Mar 2011 13:41:40 -0400 Jeremy Jackson wrote:
> 
> > Hi,
> > 
> > Sent to linux-console with no reply for over a week...
> > 
> > I ran into a problem recently on a Linux server with a remote serial 
> > console.  /sbin/init (actually Upstart) was in a state where nothing 
> > (useful) was running.  I had to power cycle the machine to get back to 
> > the boot prompt.  This has the side-effect of triggering raid rebuilds.
> > 
> > It would be nice to have what Ctrl-Alt-Del does at the VGA console with 
> > PS/2 or USB keyboard. This sends a SIGINT to PID 1, and most distros 
> > have this set to do "shutdown -r now" which attempts a clean reboot.
> 
> so C_A_D works at console via PS/2 or USB keyboard, but not on a remote
> serial console?  Could it be an issue with whatever remote/serial software
> you are using?

I believe it is simply a matter of console keymap and assigning "boot"
value to the desired combination.

> 
> > Once upon a time there was KeyboardRequest, which would send a SIGWINCH 
> > to PID 1 (when pressing Alt-UP_arrow?).  I don't see any sign of this 
> > feature in Linux 2.6.32 though.
> 
> I couldn't find it in 2.4.37 either.
> 
> Can 'loadkeys' help you any?
> 
> > Looking at the Sysrq handlers in the kernel I don't see any keystrokes 
> > that send SIGINT to PID 1 either.
> > 
> > So, I'm wondering if it makes sense to add a Sysrq key to send a signal 
> > to PID1 ?
> 
> Dmitry, any ideas?

We have SysRq bindings to unmount filesystems and reboot, isn't that
enough?

-- 
Dmitry
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