PANIC(8S)

NAME
panic - what happens when the system crashes

DESCRIPTION

This section explains what happens when the system crashes and how you can analyze crash dumps.

When the system crashes voluntarily, it displays a message of the form

    panic: why i gave up the ghost

on the console, takes a dump on a mass storage peripheral, and then invokes an automatic reboot procedure as described in reboot(8). Unless some unexpected inconsistency is encountered in the state of the file systems due to hardware or software failure, the system will then resume multiuser operations.

The system has a large number of internal consistency checks; if one of these fails, it will panic with a very short message indicating which one failed.

When the system crashes it writes (or at least attempts to write) an image of memory into the back end of the primary swap area. After the system is rebooted, you can run the program savecore(8) to preserve a copy of this core image and kernel namelist for later perusal. See savecore(8) for details.

To analyze a dump you should begin by running adb(1) with the -k flag on the core dump, as described in

The most common cause of system failures is hardware failure, which can reflect itself in different ways.

See DIAGNOSTICS for some messages that you may encounter, with some hints as to causes. In each case there is a possibility that a hardware or software error produced the message in some unexpected way.

FILES
/vmunix
    the system kernel
/etc/rc.local
    script run when the local system starts up

SEE ALSO
adb(1), old-analyze(8), reboot(8) sa(8), savecore(8)

DIAGNOSTICS
IO err in push
hard IO err in swap
    The system encountered an error trying to write to the paging device or an error in reading critical information from a disk drive. You should fix your disk if it is broken or unreliable.
timeout table overflow
    This really should not be a panic, but until the data structure is fixed, involved, running out of entries causes a crash. If this happens, you should make the timeout table bigger by changing the value of ncallout in the param.c file, and then rebuild your system.
trap type type, pid process-id, pc = program-counter, sr = status-register, context context-number
    A unexpected trap has occurred within the system; typical trap types are:
    •   Bus error
    •   Address error
    •   Illegal instruction
    •   Divide by zero
    •   Chk instruction
    •   Trapv instruction
    •   Privilege violation
    •   Trace
    •   1010 emulator trap
    •   1111 emulator trap
    •   Stack format error
    •   Uninitialized interrupt
    •   Spurious interrupt

    The favorite trap types in system crashes are ``Bus error'' or ``Address error'', indicating a wild reference. The process-id is the ID of the process running at the time of the fault, program-counter is the hexadecimal value of the program counter, status-register is the hexadecimal value of the status register, and context-number is the context that the process was running in. These problems tend to be easy to track down if they are kernel bugs since the processor stops cold, but random flakiness seems to cause this sometimes.

init died
    The system initialization process has exited. This is bad news, as no new users will then be able to log in. Rebooting is the only fix, so the system just does it right away.