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https://github.com/m7a/lp-maerct

Ma_Sys.ma Emergency Remote Control
https://github.com/m7a/lp-maerct

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Ma_Sys.ma Emergency Remote Control

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README 

        
---

section: 11

x-masysma-name: maerct

title: Ma_Sys.ma Emergency Remote Control

date: 2020/01/17 15:22:37

lang: en-US

author: ["Linux-Fan, Ma_Sys.ma ([email protected])"]

keywords: ["programs", "c", "maerct", "linux", "keyboard"]

x-masysma-version: 1.1.0

x-masysma-repository: https://www.github.com/m7a/lp-maerct

x-masysma-website: https://masysma.net/11/maerct.xhtml

x-masysma-owned: 1

x-masysma-copyright: |

  Copyright (c) 2020 Ma_Sys.ma.

  For further info send an e-mail to [email protected].

---

Name

====



`maerct` -- Ma_Sys.ma Emergency Remote Control: Kill X11 in case of hangs.



Synopsis

========



	maerct [-f] FILE



Description

===========



This program has to be run by the root user. It takes a Linux keyboard event

device, e. g. `/dev/input/event0` and grabs it exclusively. Do not run it if

you only have one keyboard attached. `-f` forks twice.



## Table of blink codes



NumLock  CapsLock  ScrollLock  Description

-------  --------  ----------  ------------------------------

slow     off       off         Program operating correctly.

fast     off       off         Program expecting input.

off      fast      off         Process `X` takes >80% CPU.

off      slow      off         RAM exceeded.

off      off       slow        Shorttime Load AVG greater 10.

off      off       fast        Command is being executed.

off      off       off         Program not operating.



## Table of possible inputs



Key  Description

---  ----------------------------------------------------------

ESC  Cancel pending operation

F1   Attempt to kill X11 process

F2   Attempt to start (and immediately terminate) new X server.

F4   Exit this program (no unlock required)

u    Press this before another operation to unlock input.



Extended Description

====================



This program is intended to run as a background service on an interactively

used machine with a second keyboard connected for the sole purpose of being

used by this program (e. g. one can install otherwise unused PS2 keyboards for

the purpose).



It then outputs a limited amount of status information in form of regular blink

codes using the three keyboard LEDs: NumLock, CapsLock and ScrollLock.



Apart from displaying status, it can serve as a remote control (thus the name)

for killing the X-server. This might be an interesting feature for users of

third-party kernel modules (e. g. NVidia drivers or VirtualBox modules) which

used to cause some X11 freezes on the machine this program was developed for.

By pressing [U], followed by [F1], one can cause the X-server to be

terminated, freeing access to the console (if it does not work, sequence [U]

followed by [F2] attempts to restart the X-server).



Be aware that similar to SysRq-codes (which may also work in such cases), this

program allows bypassing any running screensaver! In case you only want the

keyboard blinking, consider using [ma_capsblinker(11)](ma_capsblinker.xhtml)

(currently does not provide any status information, but does not need to run

on a _separate_ keyboard).



This program is provided together with an LSB init script

(`masysma-emergency-remote-control`) and a default configuration in

`/etc/default/maerct` which is actually a shellscript sourced into the init

script, allowing for host-specific configuration or any other logic.



Compilation

===========



To compile this program, a C compiler is needed e. g. as provided by Debian

package `gcc-8-base`. Additionally, the `ant` build tool is needed and can then

be invoked by running `ant`. To build the Debian package (with the necessary

dependencies installed), use `ant package`.