• r — Disables raw mode for the keyboard and sets it to XLATE (a limited keyboard modewhich does not recognize modifiers such as Alt, Ctrl, or Shift for all keys).• k — Kills all processes active in a virtual console. Also called Secure Access Key (SAK), itis often used to verify that the login prompt is spawned from init and not a trojan copydesigned to capture usernames and passwords.• b — Reboots the kernel without first unmounting file systems or syncing disks attached tothe system.• c — Crashes the system without first unmounting file systems or syncing disks attached tothe system.• o — Shuts off the system.• s — Attempts to sync disks attached to the system.• u — Attempts to unmount and remount all file systems as read-only.• p — Outputs all flags and registers to the console.• t — Outputs a list of processes to the console.• m — Outputs memory statistics to the console.• 0 through 9 — Sets the log level for the console.• e — Kills all processes except init using SIGTERM.• i — Kills all processes except init using SIGKILL.• l — Kills all processes using SIGKILL (including init). The system is unusable afterissuing this System Request Key code.• h — Displays help text.This feature is most beneficial when using a development kernel or when experiencingsystem freezes.CautionThe System Request Key feature is considered a security risk because anunattended console provides an attacker with access to the system. For thisreason, it is turned off by default.Refer to /usr/share/doc/kernel-doc-/Documentation/sysrq.txt for moreinformation about the System Request Key./proc/sys/79
