Console Input – Locking Console Input Without Screen Blanking

console

I'm looking for a method to lock/disable keyboard input into a text console (tty, no xorg) without blanking the screen. I would like to be able to monitor the on-screen progress of a long-running program (Partclone) without worrying about tampering at the keyboard (Ctrl-C, switching terminals, etc).

I'm aware of vlock, but it blanks the screen.

Best Answer

This question really intrigued me, seemed like a simple request but was tricky to find options beyond the typical xlock, vlock and xset options.

However I believe I've found 2 methods to do this.

Method #1 - cat /dev/...

The first method basically consumes /dev/tty0 so nothing else can get through.

nohup cat /dev/tty0 > /dev/null &

Method #2 - disable usbhid module

The second method involves unloading the usbhid kernel module. This will only work if you have a USB keyboard.

modprobe -r usbhid

Method #3 - grub

You can disable all USB devices using the nousb parameter to the kernel via Grub.

kernel /vmlinuz-2.6.18-128.1.1.el5 ro root=LABEL=/ console=tty0 console=ttyS1,19200n8 nousb

Related Solutions

Disable Screen Blanking on Text Console – Prevent Terminal Screen Blanking

You can verify what timeout the kernel uses for virtual console blanking via:

$ cat /sys/module/kernel/parameters/consoleblank
600

This file is read-only and the timeout is specified in seconds. The current default seems to be 10 minutes.

You can change that value with entering the following command on a virtual console (if you are inside an xterm you have to change to a virtual console via hitting e.g. Ctrl+Alt+F1).

$ setterm -blank VALUE

Where the new VALUE is specified in minutes. A value of 0 disables blanking:

$ cat /sys/module/kernel/parameters/consoleblank
600
$ setterm -blank 0
$ cat /sys/module/kernel/parameters/consoleblank
0

setterm has other powersaving related options, the most useful combination seems to be:

$ setterm -blank 0 -powersave off

Thus to permanently/automatically disable virtual console blanking on startup you can either:

add consoleblank=0 to the kernel parameters (edit grub configuration)
add the setterm -blank 0 command to an rc-local or equivalent startup script
add the setterm output to /etc/issue since /etc/issue is output on every virtual console:

# setterm -blank 0 >> /etc/issue

Choose one alternative from the above.