[SOLVED] How to disable console blanking in text mode

ShadyCraig · 01-06-2010, 10:05 AM

Hi All,

I run a custom build of linux running kernel 2.6.24 and busybox.
At the moment I'm investigating a kernel panic.

The problem is that after 10 minutes the screen is blanked, i.e. it is still on but has been turned black. If you press a key then the command prompt is shown once again, but if the kernel has crashed then this won't work and any info about the panic is inaccessible.

So I'd like to prevent the display being blanked.
I've tried booting with 'apm=off' and 'apm=off acpi=on' kernel parameters but neither had any effect.

Any help in this matter will be gratefully received.

Thanks,
Craig

slinx · 01-06-2010, 10:08 AM

Have you checked your monitor for a blanking setting? It may have a setting you can configure in the OSD.

ShadyCraig · 01-06-2010, 10:58 AM

Thanks for your reply slinx,

I've checked the OSD for the monitor and no such setting exists.

Also I'm sure it's not the monitor as when in power saving mode the power led changes to amber but it's remaining green.

Thanks again!

slacker_et · 01-06-2010, 11:06 AM

Wow ! It's been years since I had to change that setting.
But I think you may want to investigate using setterm and it's -blank argument.

Code:

SETTERM(1)                                                        Linux Programmer's Manual                                                       SETTERM(1)



NAME
       setterm - set terminal attributes

SYNOPSIS
       setterm [options]

DESCRIPTION
       setterm  writes  to standard output a character string that will invoke the specified terminal capabilities.  Where possible terminfo is consulted to
       find the string to use.  Some options however (marked "virtual consoles only" below) do not correspond to a terminfo(5) capability.  In this case, if
       the  terminal  type is "con" or "linux" the string that invokes the specified capabilities on the PC Minix virtual console driver is output.  Options
       that are not implemented by the terminal are ignored.

OPTIONS
.
.
.
.
       -blank [0-60] (virtual consoles only)
              Sets  the interval of inactivity, in minutes, after which the screen will be automatically blanked (using APM if available).  Without an argu-
              ment, defaults to 0 (disable console blanking).

--ET

ShadyCraig · 01-06-2010, 11:14 AM

Thanks slacker_et,

Unfortunately I don't have setterm on my system but I'm having a look at the source to see what it does.
I can't just compile it as everything has to be cross-compiled for this system :-(

Cheers!

ShadyCraig · 01-06-2010, 11:29 AM

I've had a look at the source code for setterm and basically it prints some special characters to the terminal.
Using the command-line version of printf it's possible to emulate it.

To set the -blank option do:

Code:

printf "\033[9;%ld]" minutes

Replace 'minutes' with a value 0-60.

In my case I used 0 to disable the blanking:

Code:

printf "\033[9;%ld]" 0

Just have to wait an see it it works (ok so far).

Thanks for the pointer slacker_et!