Re: disabling BREAK on Suns

[Gregg TeHennepe <gat@jax.org>]

On Thu, 14 Jan 1999, Brett Lemoine wrote:

> > > The only downside of using serial consoles with Suns is that Suns have
> > > the annoying habit of dropping into the ROM monitor when power to the
> > > console server is lost (they interpret this as a "break" condition).
> > > As best I can tell this is the case for any serial console hooked up
> > > to a Sun, even a dumb terminal.
> > 	
> > 	It is.  It's happened to me many times.  (Seems silly to
> > 	*have* to put your rarely used serial console terminal
> > 	on your UPS --- but that's Sun's idea of a joke on 
> > 	all of us).  What were those little Stanford boys thinking?
> 
> Sun Consulting has software for Solaris 2.6 and earlier that permits
> the changing of the character interpreted as the 'break'.  It's not
> cheap, but worth the price of not watching a couple of hundred Sun
> systems halt 'cause some idiot tripped over a power strip.  Ask
> your Sun sales rep about Sun Consulting's ZSBRK package.

>From the Sol 2.6 man page for kbd(1):

     The keyboard abort sequence (L1-A or STOP-A on the  keyboard
     and  BREAK  on  the serial console input device on most sys-
     tems) effect may only be changed by the superuser, using the
     -a option.

     On most systems, the default effect of  the  keyboard  abort
     sequence  is  to  suspend the operating system and enter the
     debugger or the monitor.  Some  systems  have  key  switches
     with  a  'secure' position. On these systems, the key switch
     in the 'secure' position, overrides any software default set
     with this command.

     If you want  to  permanently  change  the  software  default
     effect of the keyboard abort sequence, you can add or change
     the current value of  the  KEYBOARD_ABORT  variable  to  the
     value    disable    in    the    keyboard    default   file,
     /etc/default/kbd, as shown here.

          KEYBOARD_ABORT=disable

     Then, run the command 'kbd -i' to change  the  current  set-
     ting.   Valid  settings for this value are the values enable
     and disable.  Other values are ignored.  If the variable  is
     not specified in the default file, the setting is unchanged.

[...]

     -a enable/disable state
                       Enable  or  disable  the  keyboard   abort
                       sequence effect.
                       By  default,  a  keyboard  abort  sequence
                       (typically, Stop-A or L1-A on the keyboard
                       and BREAK on the  serial  console  device)
                       suspends the Operating System on most sys-
                       tems.   This  default  behavior   can   be
                       changed using this option. This option can
                       only be used by the superuser.

                       enable
                            Enable the default effect of the key-
                            board  abort  sequence,  which  is to
                            suspend  the  operating  system   and
                            enter the debugger or the monitor.

                       disable
                            Disable the default effect and ignore
                            keyboard abort sequences.


I've used it several times to rearrange cabling and configurations on a
console switch without bringing the system down. Note this is not available in
Sol 2.5.1.

Hope this helps... - Gregg

Gregg TeHennepe  | Unix Systems Administrator  | The Jackson Laboratory
gat@jax.org      | http://a.jax.org/~gat       | Bar Harbor, Maine  USA