What is the SysRq facility and how do I use it?
The SysRq facility is one of the best (and sometimes the only) way to determine what a machine is really doing. When triggered, SysRq will send a signal requesting some diagnostic information to the operating system kernel.
Where is SysRq button?
The SysRq key is located near the Scroll Lock key on your keyboard – the Sys Rq key is generally the same as your Print Screen key. The “magic” SysRq combination is Alt+SysRq.
What is kernel Yama?
Yama is a Linux Security Module that collects system-wide DAC security protections that are not handled by the core kernel itself.
How do I restart Sysctl conf?
How to reload sysctl. conf variables on Linux
- Read variable from command line. Type the following command.
- Write variable from command line. The syntax is:
- Reload settings from all system configuration files. Type the following command to reload settings from config files without rebooting the box:
- Persistent configuration.
How to get TXT output from SysRq?
One method of getting txt output regarding how your system is using sysrq is to apply sysrq commands from tty (when system not suffering from locks/freezes). Doing this may indicate sysrq has not been completely disabled but is using bitmask 176.
How to re-enable SysRq at boot time?
To re-enable it at boot time, you have to edit /etc/sysctl.d/10-magic-sysrq.conf file. ie uncommenting this line will enable all functions of sysrq: When running a kernel with SysRq compiled in, /proc/sys/kernel/sysrq controls the functions allowed to be invoked via the SysRq key.
Why is SysRq enabled by default in Ubuntu?
Consider this bug description found at LaunchPad Bug 194676: By default SysRq is enabled by default on Ubuntu desktop systems which is invaluable when a system has locked up and you want to stop it as gently as possible or debug the issue.
Why is Alt + SysRq disabled in sysctl?
Alt+SysRq has been disabled to fix a bug. The disabling of Magic-SysRq was considered a bug itself and it has since been re-enabled ( #1025467 ). If it is still disabled for you, you can re-enable it: Edit the file /etc/sysctl.conf to include the line