'r' - Turns off keyboard raw mode and sets it to XLATE.



'k' - Secure Access Key (SAK) Kills all programs on the current virtual

console. NOTE: See important comments below in SAK section.



'b' - Will immediately reboot the system without syncing or unmounting

your disks.



'o' - Will shut your system off (if configured and supported).



's' - Will attempt to sync all mounted filesystems.



'u' - Will attempt to remount all mounted filesystems read-only.



'p' - Will dump the current registers and flags to your console.



't' - Will dump a list of current tasks and their information to your

console.



'm' - Will dump current memory info to your console.



'0'-'9' - Sets the console log level, controlling which kernel messages

will be printed to your console. ('0', for example would make

it so that only emergency messages like PANICs or OOPSes would

make it to your console.)



'e' - Send a SIGTERM to all processes, except for init.



'i' - Send a SIGKILL to all processes, except for init.



'l' - Send a SIGKILL to all processes, INCLUDING init. (Your system

will be non-functional after this.)



'h' - Will display help ( actually any other key than those listed

above will display help. but 'h' is easy to remember :-

In sintesi ti consiglio
quando il sistema s'impalla
ctrl+alt+sysrq+s (fa il sync)
ctrl+alt+sysrq+u (smonta i dischi)
ctrl+alt+sysrq+b (reboota)