Sometimes Kernel-Panics happen. It's awful, and nobody wants them, but sh** happens. Sometimes it's because of a hardware problem, sometimes it's just a software problem. Mostly the system hangs then and administratos have to reboot the system. But it is possible to tell Linux to automatic reboot when a kernel-panic happens...
A sysctl-key existists named "kernel.panic". We can set a value, how long the system will wait until it reboots. Just edit the /etc/sysctl.conf:
kernel.panic = 30
Now we can use sysctl to take over the changes:
dr@tardis:/# sysctl -p kernel.panic = 30
Finish, but there is something more connected to this topic... The Kernel-Documentations are very thrilling bed-lectures for all the geeks who love to read crime novels. In those docs there is a file called "sysrq.txt". I'll just post all the very interesting paragraphs here:
Linux Magic System Request Key Hacks Documentation for sysrq.c * What is the magic SysRq key? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ It is a 'magical' key combo you can hit which the kernel will respond to regardless of whatever else it is doing, unless it is completely locked up. * How do I enable the magic SysRq key? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ You need to say "yes" to 'Magic SysRq key (CONFIG_MAGIC_SYSRQ)' when configuring the kernel. When running a kernel with SysRq compiled in, /proc/sys/kernel/sysrq controls the functions allowed to be invoked via the SysRq key. The default value in this file is set by the CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE config symbol, which itself defaults to 1. Here is the list of possible values in /proc/sys/kernel/sysrq: 0 - disable sysrq completely 1 - enable all functions of sysrq >1 - bitmask of allowed sysrq functions (see below for detailed function description): 2 = 0x2 - enable control of console logging level 4 = 0x4 - enable control of keyboard (SAK, unraw) 8 = 0x8 - enable debugging dumps of processes etc. 16 = 0x10 - enable sync command 32 = 0x20 - enable remount read-only 64 = 0x40 - enable signalling of processes (term, kill, oom-kill) 128 = 0x80 - allow reboot/poweroff 256 = 0x100 - allow nicing of all RT tasks You can set the value in the file by the following command: echo "number" >/proc/sys/kernel/sysrq The number may be written here either as decimal or as hexadecimal with the 0x prefix. CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE must always be written in hexadecimal. Note that the value of /proc/sys/kernel/sysrq influences only the invocation via a keyboard. Invocation of any operation via /proc/sysrq-trigger is always allowed (by a user with admin privileges). * How do I use the magic SysRq key? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ On x86 - You press the key combo 'ALT-SysRq-
'. Note - Some keyboards may not have a key labeled 'SysRq'. The 'SysRq' key is also known as the 'Print Screen' key. Also some keyboards cannot handle so many keys being pressed at the same time, so you might have better luck with "press Alt", "press SysRq", "release SysRq", "press ", release everything. On SPARC - You press 'ALT-STOP- ', I believe. On the serial console (PC style standard serial ports only) - You send a BREAK, then within 5 seconds a command key. Sending BREAK twice is interpreted as a normal BREAK. On PowerPC - Press 'ALT - Print Screen (or F13) - , Print Screen (or F13) - may suffice. On other - If you know of the key combos for other architectures, please let me know so I can add them to this section. On all - write a character to /proc/sysrq-trigger. e.g.: echo t > /proc/sysrq-trigger * What are the 'command' keys? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 'b' - Will immediately reboot the system without syncing or unmounting your disks. 'c' - Will perform a system crash by a NULL pointer dereference. A crashdump will be taken if configured. 'd' - Shows all locks that are held. 'e' - Send a SIGTERM to all processes, except for init. 'f' - Will call oom_kill to kill a memory hog process. 'g' - Used by kgdb (kernel debugger) 'h' - Will display help (actually any other key than those listed here will display help. but 'h' is easy to remember :-) 'i' - Send a SIGKILL to all processes, except for init. 'j' - Forcibly "Just thaw it" - filesystems frozen by the FIFREEZE ioctl. 'k' - Secure Access Key (SAK) Kills all programs on the current virtual console. NOTE: See important comments below in SAK section. 'l' - Shows a stack backtrace for all active CPUs. 'm' - Will dump current memory info to your console. 'n' - Used to make RT tasks nice-able 'o' - Will shut your system off (if configured and supported). 'p' - Will dump the current registers and flags to your console. 'q' - Will dump per CPU lists of all armed hrtimers (but NOT regular timer_list timers) and detailed information about all clockevent devices. 'r' - Turns off keyboard raw mode and sets it to XLATE. 's' - Will attempt to sync all mounted filesystems. 't' - Will dump a list of current tasks and their information to your console. 'u' - Will attempt to remount all mounted filesystems read-only. 'v' - Forcefully restores framebuffer console 'v' - Causes ETM buffer dump [ARM-specific] 'w' - Dumps tasks that are in uninterruptable (blocked) state. 'x' - Used by xmon interface on ppc/powerpc platforms. Show global PMU Registers on sparc64. 'y' - Show global CPU Registers [SPARC-64 specific] 'z' - Dump the ftrace buffer '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.)